diff --git a/.travis.yml b/.travis.yml
index 3fed41b..5c69187 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -3,65 +3,140 @@
 language: cpp
 sudo: false
 
+cache:
+  directories:
+    - ${TRAVIS_BUILD_DIR}/deps/cmake
+    - ${TRAVIS_BUILD_DIR}/deps/llvm-3.5.2/install
+    - ${TRAVIS_BUILD_DIR}/deps/llvm-3.6.2/install
+    - ${TRAVIS_BUILD_DIR}/deps/llvm-3.7.1/install
+    - ${TRAVIS_BUILD_DIR}/deps/llvm-3.8.1/install
+    - ${TRAVIS_BUILD_DIR}/deps/llvm-3.9.0/install
+
 matrix:
   include:
-    - env: COMPILER=clang++-3.6 BUILD_TYPE=Debug CLANG=1
+    - env: BUILD_TYPE=Debug
+      os: osx
+      osx_image: xcode8
       compiler: clang
+    - env: BUILD_TYPE=Release
+      os: osx
+      osx_image: xcode8
+      compiler: clang
+    - env: CLANG_VERSION=3.6 BUILD_TYPE=Debug
+      os: linux
       addons: &clang36
         apt:
           packages:
             - clang-3.6
-            - cmake
             - g++-5
           sources: &sources
             - ubuntu-toolchain-r-test
             - llvm-toolchain-precise-3.6
-            - kalakris-cmake
-    - env: COMPILER=clang++-3.6 BUILD_TYPE=Release CLANG=1
-      compiler: clang
+    - env: CLANG_VERSION=3.6 BUILD_TYPE=Release
+      os: linux
       addons: *clang36
-    - env: COMPILER=g++-5 BUILD_TYPE=Debug
-      compiler: gcc
+    - env: CLANG_VERSION=3.7 BUILD_TYPE=Debug
+      os: linux
+      addons: &clang37
+        apt:
+          packages:
+            - clang-3.7
+            - g++-5
+          sources: &sources
+            - ubuntu-toolchain-r-test
+            - llvm-toolchain-precise-3.7
+    - env: CLANG_VERSION=3.7 BUILD_TYPE=Release
+      os: linux
+      addons: *clang37
+    - env: CLANG_VERSION=3.8 BUILD_TYPE=Debug
+      os: linux
+      addons: &clang38
+        apt:
+          packages:
+            - clang-3.8
+            - g++-5
+          sources: &sources
+            - ubuntu-toolchain-r-test
+            - llvm-toolchain-precise-3.8
+    - env: CLANG_VERSION=3.8 BUILD_TYPE=Release
+      os: linux
+      addons: *clang38
+    - env: GCC_VERSION=5 BUILD_TYPE=Debug
+      os: linux
       addons: &gcc5
         apt:
           packages: g++-5
           sources: *sources
-    - env: COMPILER=g++-5 BUILD_TYPE=Release
-      compiler: gcc
+    - env: GCC_VERSION=5 BUILD_TYPE=Release
+      os: linux
       addons: *gcc5
+    - env: GCC_VERSION=6 BUILD_TYPE=Debug
+      os: linux
+      addons: &gcc6
+        apt:
+          packages: g++-6
+          sources: *sources
+    - env: GCC_VERSION=6 BUILD_TYPE=Release
+      os: linux
+      addons: *gcc6
 
 install:
-  - which $COMPILER
+  - if [[ -n "$CLANG_VERSION" ]]; then export CXX=clang++-$CLANG_VERSION CC=clang-$CLANG_VERSION; fi
+  - if [[ -n "$GCC_VERSION" ]]; then export CXX=g++-$GCC_VERSION CC=gcc-$GCC_VERSION; fi
+  - JOBS=2
   - DEPS_DIR="${TRAVIS_BUILD_DIR}/deps"
-  - mkdir ${DEPS_DIR} && cd ${DEPS_DIR}
+  - mkdir -p "${DEPS_DIR}" && cd "${DEPS_DIR}"
+
+  ############################################################################
+  # Install a recent CMake (unless already installed on OS X)
+  ############################################################################
   - |
-    if [[ "$CLANG" == 1 && "${TRAVIS_OS_NAME}" == "linux" && "${STDLIB}" != "libstdc++" ]]; then
-      if [[ "${COMPILER}" == "clang++-3.5" ]]; then LLVM_VERSION="3.5.2"; fi
-      if [[ "${COMPILER}" == "clang++-3.6" ]]; then LLVM_VERSION="3.6.2"; fi
-      if [[ "${COMPILER}" == "clang++-3.7" ]]; then LLVM_VERSION="3.7.0"; fi
+    if [[ "${TRAVIS_OS_NAME}" == "linux" ]]; then
+      if [[ -z "$(ls -A ${DEPS_DIR}/cmake/bin)" ]]; then
+        CMAKE_URL="https://cmake.org/files/v3.6/cmake-3.6.2-Linux-x86_64.tar.gz"
+        mkdir -p cmake && travis_retry wget --no-check-certificate --quiet -O - "${CMAKE_URL}" | tar --strip-components=1 -xz -C cmake
+      fi
+      export PATH="${DEPS_DIR}/cmake/bin:${PATH}"
+    else
+      if ! brew ls --version cmake &>/dev/null; then brew install cmake; fi
+    fi
+
+  ############################################################################
+  # [linux]: Install the right version of libc++
+  ############################################################################
+  - |
+    if [[ -n "$CLANG_VERSION" && "${TRAVIS_OS_NAME}" == "linux" && "${STDLIB}" != "libstdc++" ]]; then
+      if [[ "$CLANG_VERSION" == "3.5" ]]; then LLVM_VERSION="3.5.2"; fi
+      if [[ "$CLANG_VERSION" == "3.6" ]]; then LLVM_VERSION="3.6.2"; fi
+      if [[ "$CLANG_VERSION" == "3.7" ]]; then LLVM_VERSION="3.7.1"; fi
+      if [[ "$CLANG_VERSION" == "3.8" ]]; then LLVM_VERSION="3.8.1"; fi
+      if [[ "$CLANG_VERSION" == "3.9" ]]; then LLVM_VERSION="3.9.0"; fi
+      LLVM_ROOT="${DEPS_DIR}/llvm-${LLVM_VERSION}"
       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 --quiet -O - ${LLVM_URL} | tar --strip-components=1 -xJ -C llvm
-      travis_retry wget --quiet -O - ${LIBCXX_URL} | tar --strip-components=1 -xJ -C llvm/projects/libcxx
-      travis_retry wget --quiet -O - ${LIBCXXABI_URL} | tar --strip-components=1 -xJ -C llvm/projects/libcxxabi
-      (cd llvm/build && cmake .. -DCMAKE_INSTALL_PREFIX=${DEPS_DIR}/llvm/install -DCMAKE_CXX_COMPILER=clang++)
-      (cd llvm/build/projects/libcxx && make install -j2)
-      (cd llvm/build/projects/libcxxabi && make install -j2)
-      export CXXFLAGS="-I ${DEPS_DIR}/llvm/install/include/c++/v1"
-      export LDFLAGS="-L ${DEPS_DIR}/llvm/install/lib -l c++ -l c++abi"
-      export LD_LIBRARY_PATH="${LD_LIBRARY_PATH}:${DEPS_DIR}/llvm/install/lib"
+      if [[ -z "$(ls -A ${LLVM_ROOT}/install/include)" ]]; then
+        mkdir -p "${LLVM_ROOT}" "${LLVM_ROOT}/build" "${LLVM_ROOT}/projects/libcxx" "${LLVM_ROOT}/projects/libcxxabi"
+        travis_retry wget --quiet -O - "${LLVM_URL}" | tar --strip-components=1 -xJ -C "${LLVM_ROOT}"
+        travis_retry wget --quiet -O - "${LIBCXX_URL}" | tar --strip-components=1 -xJ -C "${LLVM_ROOT}/projects/libcxx"
+        travis_retry wget --quiet -O - "${LIBCXXABI_URL}" | tar --strip-components=1 -xJ -C "${LLVM_ROOT}/projects/libcxxabi"
+        (cd "${LLVM_ROOT}/build" && cmake .. -DCMAKE_CXX_COMPILER="$CXX" -DCMAKE_C_COMPILER="$CC" -DCMAKE_INSTALL_PREFIX="${LLVM_ROOT}/install" -DCMAKE_BUILD_TYPE=$BUILD_TYPE)
+        (cd "${LLVM_ROOT}/build/projects/libcxx" && make install -j$JOBS)
+        (cd "${LLVM_ROOT}/build/projects/libcxxabi" && make install -j$JOBS)
+      fi
+      export CXXFLAGS="-I ${LLVM_ROOT}/install/include/c++/v1"
+      export LDFLAGS="-L ${LLVM_ROOT}/install/lib -lc++ -lc++abi"
+      export LD_LIBRARY_PATH="${LD_LIBRARY_PATH}:${LLVM_ROOT}/install/lib"
     fi
 
 before_script:
-  - cd ${TRAVIS_BUILD_DIR}
-  - cmake -H. -Bb -DCMAKE_CXX_COMPILER=$COMPILER -DCMAKE_INSTALL_PREFIX=$PWD/o -DCMAKE_BUILD_TYPE=$BUILD_TYPE
-  - cmake --build b
+  - cd "${TRAVIS_BUILD_DIR}"
+  - cmake . -Bbuild -DCMAKE_CXX_COMPILER="$CXX" -DCMAKE_C_COMPILER="$CC" -DCMAKE_BUILD_TYPE=$BUILD_TYPE
+  - cmake --build build -- -j$JOBS
 
 script:
-  - cd b
-  - ctest
+  - cd build
+  - ctest --output-on-failure -j$JOBS
 
 notifications:
   email: false