This PR replaces UnitTest-cpp with Catch. Catch is downloaded
using cmake's ExternalProject_Add and installed into the
include directory as it's a header only library.
Signed-off-by: Rian Quinn <“rianquinn@gmail.com”>
* CI updates:
Travis: use cmake 3.7
Appveyor: Add .appveyor.yml config, test VS2013/VS2015/VS2017 x86/x64 Debug/Release.
* Drop VS2013 support from AppVeyor.