Added support for CI AppVeyor

I have a node.js project that needs to be built and tested on a Windows machine. In [AppVeyor](http://www.appveyor.com) CI this is possible. But there is an issue with getting codeclimate to accept the coverage report when sending it from AppVeyor. There are detached HEADs and other stuff. So I thought it might help if codeclimate gets the proper CI info, i.e. branch and commit_sha.

Added a test as well.