Add continuous testing for Windows build, or remove it
There's currently no continuous testing for the Windows CMake build and I don't have any Windows machines available for manual testing. There needs to be some kind of CI setup for Windows before the next release or otherwise it should be removed. It makes no sense to keep around build files and rockspecs for a half-supported and barely tested platform.
I'm leaning towards removing it at the moment, since I have no knowledge of how to set up Appveyor and currently very little time or inclination to learn.