TST: Windows CI Testing using AppVeyor

Continuous Integration on Windows using [AppVeyor](http://www.appveyor.com/).
Actually, that won't work, because not all of the requirements are available in the Wheelhouse.  How about `pip install wheel`, `pip install -v numpy scipy cython --find-links=...`, `pip install -v -r requirements.txt`.  That way we are explicit while being flexible to the other requirements.