diff --git a/.travis.yml b/.travis.yml
deleted file mode 100644
index a57955c..0000000
--- a/.travis.yml
+++ /dev/null
@@ -1,337 +0,0 @@
-
-language: cpp
-notifications:
-  email: false
-
-# Use Linux unless specified otherwise
-os: linux
-dist: bionic
-
-cache:
-  directories:
-    - ${TRAVIS_BUILD_DIR}/deps
-
-stages:
-  - name: Latest     # Compiler with the latest major version
-  - name: Previous   # Compilers with the major version Latest - 1
-  - name: Validation # run other jobs
-
-jobs:
-  include:
-
-    ##########################################################################
-    # Validate CMake configuration
-    ##########################################################################
-
-    - name: CMake 3.1.3 - latest
-      stage: Validation
-      env: &CMAKE_VERSION_LIST
-      - CMAKE_VERSION: '"3.17.0 3.16.5 3.15.7 3.14.7 3.13.5 3.12.4 3.11.4 3.10.3 3.9.6 3.8.2 3.7.2 3.6.3 3.5.2 3.4.3 3.3.2 3.2.3 3.1.3"'
-      - GSL_CXX_STANDARD: 14
-      addons: # Get latest release (candidate)
-        apt:
-          sources:
-          - sourceline: 'deb https://apt.kitware.com/ubuntu/ bionic main'
-            key_url: 'https://apt.kitware.com/keys/kitware-archive-latest.asc'
-          - sourceline: 'deb https://apt.kitware.com/ubuntu/ bionic-rc main'
-          packages:
-          - cmake
-      script:
-      - |
-        cd ./build
-        ( set -eu
-          for CMAKE in ${CMAKE_path[@]}; do test_CMake_generate $CMAKE; done
-          export CXX=clang++
-          for CMAKE in ${CMAKE_path[@]}; do test_CMake_generate $CMAKE; done
-        )
-
-    - name: CMake 3.2.3 - 3.17.0
-      stage: Validation
-      os: osx
-      osx_image: xcode11.3
-      env:
-      - CMAKE_VERSION: '"3.17.0 3.16.5 3.15.7 3.14.7 3.13.5 3.12.4 3.11.4 3.10.3 3.9.6 3.8.2 3.7.2 3.6.3 3.5.2 3.4.3 3.3.2 3.2.3"'
-      script:
-      - |
-        cd ./build
-        ( set -eu
-          for CMAKE in ${CMAKE_path[@]}; do test_CMake_generate $CMAKE; done
-        )
-
-    ##########################################################################
-    # AppleClang on OSX
-    ##########################################################################
-
-
-
-    # Xcode 10.3
-    - name: AppleClang Xcode-10.3 C++14 Debug
-      stage: Previous
-      env: BUILD_TYPE=Debug GSL_CXX_STANDARD=14
-      os: osx
-      osx_image: xcode10.3 # AppleClang 10.0.1 same compiler as Xcode 10.2
-    - name: AppleClang Xcode-10.3 C++14 Release
-      env: BUILD_TYPE=Release GSL_CXX_STANDARD=14
-      os: osx
-      osx_image: xcode10.3
-    - name: AppleClang Xcode-10.3 C++17 Debug
-      env: BUILD_TYPE=Debug GSL_CXX_STANDARD=17
-      os: osx
-      osx_image: xcode10.3
-    - name: AppleClang Xcode-10.3 C++17 Release
-      env: BUILD_TYPE=Release GSL_CXX_STANDARD=17
-      os: osx
-      osx_image: xcode10.3
-
-
-    # Xcode 11.4
-    - name: AppleClang Xcode-11.4 C++17 Debug
-      stage: Latest
-      env: BUILD_TYPE=Debug GSL_CXX_STANDARD=17
-      os: osx
-      osx_image: xcode11.4
-    - name: AppleClang Xcode-11.4 C++17 Release
-      env: BUILD_TYPE=Release GSL_CXX_STANDARD=17
-      os: osx
-      osx_image: xcode11.4
-    - name: AppleClang Xcode-11.4 C++14 Debug
-      env: BUILD_TYPE=Debug GSL_CXX_STANDARD=14
-      os: osx
-      osx_image: xcode11.4
-    - name: AppleClang Xcode-11.4 C++14 Release
-      env: BUILD_TYPE=Release GSL_CXX_STANDARD=14
-      os: osx
-      osx_image: xcode11.4
-
-    ##########################################################################
-    # Clang on Linux
-    ##########################################################################
-
-    # Clang 9
-    - name: Clang-9 C++14 Debug
-      stage: Previous
-      env: CXX=clang++-9 BUILD_TYPE=Debug GSL_CXX_STANDARD=14
-      addons: &clang9
-        apt:
-          sources:
-          - sourceline: 'deb http://apt.llvm.org/bionic/ llvm-toolchain-bionic-9 main'
-            key_url: https://apt.llvm.org/llvm-snapshot.gpg.key
-          packages:
-          - clang-9
-    - name: Clang-9 C++14 Release
-      env: CXX=clang++-9 BUILD_TYPE=Release GSL_CXX_STANDARD=14
-      addons: *clang9
-    - name: Clang-9 C++17 Debug
-      env: CXX=clang++-9 BUILD_TYPE=Debug GSL_CXX_STANDARD=17
-      addons: *clang9
-    - name: Clang-9 C++17 Release
-      env: CXX=clang++-9 BUILD_TYPE=Release GSL_CXX_STANDARD=17
-      addons: *clang9
-
-    # Clang 10
-    - name: Clang-10 C++14 Debug
-      stage: Latest
-      env: CXX=clang++-10 BUILD_TYPE=Debug GSL_CXX_STANDARD=14
-      addons: &clang10
-        apt:
-          sources:
-          - sourceline: 'deb http://apt.llvm.org/bionic/ llvm-toolchain-bionic-10 main'
-            key_url: https://apt.llvm.org/llvm-snapshot.gpg.key
-          packages:
-          - clang-10
-    - name: Clang-10 C++14 Release
-      env: CXX=clang++-10 BUILD_TYPE=Release GSL_CXX_STANDARD=14
-      addons: *clang10
-    - name: Clang-10 C++17 Debug
-      env: CXX=clang++-10 BUILD_TYPE=Debug GSL_CXX_STANDARD=17
-      addons: *clang10
-    - name: Clang-10 C++17 Release
-      env: CXX=clang++-10 BUILD_TYPE=Release GSL_CXX_STANDARD=17
-      addons: *clang10
-
-    ##########################################################################
-    # GCC on Linux
-    ##########################################################################
-
-    # GCC 8
-    - name: GCC-8 C++14 Debug
-      stage: Previous
-      env: CXX=g++-8 BUILD_TYPE=Debug GSL_CXX_STANDARD=14
-      addons: &gcc8
-        apt:
-          packages: g++-8
-    - name: GCC-8 C++14 Release
-      env: CXX=g++-8 BUILD_TYPE=Release GSL_CXX_STANDARD=14
-      addons: *gcc8
-    - name: GCC-8 C++17 Debug
-      env: CXX=g++-8 BUILD_TYPE=Debug GSL_CXX_STANDARD=17
-      addons: *gcc8
-    - name: GCC-8 C++17 Release
-      env: CXX=g++-8 BUILD_TYPE=Release GSL_CXX_STANDARD=17
-      addons: *gcc8
-
-    # GCC 9
-    - name: GCC-9 C++14 Debug
-      stage: Latest
-      env: CXX=g++-9 BUILD_TYPE=Debug GSL_CXX_STANDARD=14
-      addons: &gcc9
-        apt:
-          sources:
-          - sourceline: ppa:ubuntu-toolchain-r/test
-          packages:
-          - g++-9
-    - name: GCC-9 C++14 Release
-      env: CXX=g++-9 BUILD_TYPE=Release GSL_CXX_STANDARD=14
-      addons: *gcc9
-    - name: GCC-9 C++17 Debug
-      env: CXX=g++-9 BUILD_TYPE=Debug GSL_CXX_STANDARD=17
-      addons: *gcc9
-    - name: GCC-9 C++17 Release
-      env: CXX=g++-9 BUILD_TYPE=Release GSL_CXX_STANDARD=17
-      addons: *gcc9
-
-before_install:
-  - |
-    # Configuration
-    JOBS=2 # Travis machines have 2 cores
-    # Dependencies required by the CI (cached directory)
-    DEPS_DIR="${TRAVIS_BUILD_DIR}/deps"
-  - |
-    # Setup
-    mkdir -p "${DEPS_DIR:?}" && cd "${DEPS_DIR:?}"
-    mkdir -p ~/tools && cd ~/tools
-    if [[ ${TRAVIS_OS_NAME:?} == "osx" ]]; then
-      export PATH="/usr/local/opt/coreutils/libexec/gnubin:$PATH"
-    fi
-  - |
-    # Helper functions
-    # usage: if [[ $(check_url '<url>') ]]; then ...
-    function check_url {( set +e
-      if [[ "$1" =~ 'github.com' ]]; then # check for first byte
-        if curl --fail --silent --output /dev/null --connect-timeout 12 --range 0-0 "$1"
-        then echo true; fi
-      else # request head
-        if curl --fail --silent --output /dev/null --connect-timeout 12 --head "$1"
-        then echo true; fi
-      fi
-      return
-    )}
-
-install:
-  ############################################################################
-  # Install a different CMake version (or several)
-  ############################################################################
-  - |
-    # Install CMake versions
-    ( set -euo pipefail
-      if [[ ${CMAKE_VERSION:-} ]]; then
-        if [[ "${TRAVIS_OS_NAME}" == "linux" ]]; then
-          OS="Linux"; EXT="sh"
-          if [[ ! ("${CMAKE_VERSION:-}" =~ .+[' '].+) ]]; then
-            # Single entry -> default CMake version
-            CMAKE_DEFAULT_DIR="/usr/local"
-          fi
-        elif [[ "${TRAVIS_OS_NAME}" == "osx" ]]; then OS="Darwin"; EXT="tar.gz"
-        else echo "CMake install not supported for this OS."; exit 1
-        fi
-        CMAKE_INSTALLER="install-cmake.${EXT}"
-      fi
-      for VERSION in ${CMAKE_VERSION:-}; do
-        CMAKE_URL="https://github.com/Kitware/CMake/releases/download/v${VERSION}/cmake-${VERSION}-${OS}-x86_64.${EXT}"
-        if [[ $(check_url "$CMAKE_URL") ]]; then
-          curl -sSL ${CMAKE_URL} -o ${CMAKE_INSTALLER}
-          CMAKE_DIR="${CMAKE_DEFAULT_DIR:-"${HOME}/tools/cmake-${VERSION}"}"
-          mkdir -p ${CMAKE_DIR}
-          if [[ "${TRAVIS_OS_NAME}" == "linux" ]]; then
-            chmod +x ${CMAKE_INSTALLER}
-            sudo ./${CMAKE_INSTALLER} --prefix=${CMAKE_DIR} --skip-license
-          else # OSX
-            mkdir -p ./CMake_tmp
-            tar --extract --gzip --file=${CMAKE_INSTALLER} --directory=./CMake_tmp
-            mv ./CMake_tmp/*/CMake.app/Contents/* ${CMAKE_DIR}
-          fi
-          rm --recursive --force ./CMake_tmp ${CMAKE_INSTALLER}
-        else echo 'Invalid url!'; echo "Version: ${VERSION}"
-        fi
-      done
-    )
-    if [[ ${CMAKE_VERSION:-} && "${TRAVIS_OS_NAME:?}" == "osx" && ! ("${CMAKE_VERSION:-}" =~ .+[' '].+) ]]
-    then # Single entry -> default CMake version
-      export PATH=${HOME}/tools/cmake-${CMAKE_VERSION:?}/bin:$PATH
-    fi
-    CMAKE_path=("cmake") # start with installed CMake version
-    for VERSION in ${CMAKE_VERSION:-}; do
-      tmp_path="$HOME/tools/cmake-${VERSION:?}/bin/cmake"
-      if [[ -x "$(command -v ${tmp_path:?})" ]]; then CMAKE_path+=("${tmp_path:?}"); fi
-    done
-    function test_CMake_generate {
-      # $1: cmake or full path to cmake
-      shopt -s extglob
-      if [[ "$1" == "cmake" || -x "$(command -v $1)" && "$1" =~ .*cmake$ ]]; then
-        echo "----------------"
-        $1 --version
-        echo "Configuration = ${BUILD_TYPE:-Debug}"
-        $1 -DCMAKE_BUILD_TYPE=${BUILD_TYPE:-Debug} ${CMAKE_GEN_FLAGS[@]:?} ..
-        rm -rf !(tests/googletest-*)
-        if [[ ! ${BUILD_TYPE:-} ]]; then echo "" && echo "Configuration = Release"
-          $1 -DCMAKE_BUILD_TYPE=Release ${CMAKE_GEN_FLAGS[@]:?} ..
-          rm -rf !(tests/googletest-*)
-        fi
-      else echo "Non existing command: $1"
-      fi
-    }
-  - |
-    # CMake wrapper (Trusty, Xenial & Bionic); restore default behaviour.
-    if [[ "${TRAVIS_OS_NAME:?}" == "linux" &&
-          "$(lsb_release --codename)" =~ (trusty|xenial|bionic)$ ]]
-    then
-      if [[ -x $(command -v /usr/local/bin/cmake) ]]; then
-        function cmake { command /usr/local/bin/cmake $@; }
-      elif [[ -x $(command -v /usr/bin/cmake) ]]; then
-        function cmake { command /usr/bin/cmake $@; }
-      fi
-    fi
-
-  ############################################################################
-  # [linux]: Install the right version of libc++
-  # Based on https://github.com/ldionne/hana/blob/master/.travis.yml
-  ############################################################################
-  - |
-    LLVM_INSTALL=${DEPS_DIR:?}/llvm/install
-    # if in linux and compiler clang and llvm not installed
-    if [[ "${TRAVIS_OS_NAME:?}" == "linux" && "${CXX%%+*}" == "clang" && -n "$(ls -A ${LLVM_INSTALL:?})" ]]; then
-      if   [[ "${CXX}" == "clang++-3.6" ]]; then LLVM_VERSION="3.6.2";
-      elif [[ "${CXX}" == "clang++-3.7" ]]; then LLVM_VERSION="3.7.1";
-      elif [[ "${CXX}" == "clang++-3.8" ]]; then LLVM_VERSION="3.8.1";
-      elif [[ "${CXX}" == "clang++-3.9" ]]; then LLVM_VERSION="3.9.1";
-      fi
-      LLVM_URL="http://llvm.org/releases/${LLVM_VERSION}/llvm-${LLVM_VERSION}.src.tar.xz"
-      LIBCXX_URL="http://llvm.org/releases/${LLVM_VERSION}/libcxx-${LLVM_VERSION}.src.tar.xz"
-      LIBCXXABI_URL="http://llvm.org/releases/${LLVM_VERSION}/libcxxabi-${LLVM_VERSION}.src.tar.xz"
-      mkdir -p llvm llvm/build llvm/projects/libcxx llvm/projects/libcxxabi
-      travis_retry wget -O - ${LLVM_URL} | tar --strip-components=1 -xJ -C llvm
-      travis_retry wget -O - ${LIBCXX_URL} | tar --strip-components=1 -xJ -C llvm/projects/libcxx
-      travis_retry wget -O - ${LIBCXXABI_URL} | tar --strip-components=1 -xJ -C llvm/projects/libcxxabi
-      (cd llvm/build && cmake .. -DCMAKE_INSTALL_PREFIX=${LLVM_INSTALL})
-      (cd llvm/build/projects/libcxx && make install -j2)
-      (cd llvm/build/projects/libcxxabi && make install -j2)
-      export CXXFLAGS="-isystem ${LLVM_INSTALL}/include/c++/v1"
-      export LDFLAGS="-L ${LLVM_INSTALL}/lib -l c++ -l c++abi"
-      export LD_LIBRARY_PATH="${LD_LIBRARY_PATH}:${LLVM_INSTALL}/lib"
-    fi
-
-before_script:
-  - |
-    cd "${TRAVIS_BUILD_DIR:?}"
-    mkdir build && cd build
-    if [[ ${GSL_CXX_STANDARD:-} ]]; then
-      CMAKE_GEN_FLAGS=("-DGSL_CXX_STANDARD=$GSL_CXX_STANDARD")
-    fi
-    CMAKE_GEN_FLAGS+=("-Wdev -Werror=dev --warn-uninitialized")
-
-script:
-  # generate build files
-  - cmake .. -DCMAKE_BUILD_TYPE=${BUILD_TYPE:?} ${CMAKE_GEN_FLAGS[@]:?}
-  # build and run tests
-  - cmake --build . -- -j${JOBS}
-  - ctest --output-on-failure -j${JOBS}