Support MSVC

Not ready to merge yet, just for discussion and to get the tests.

The tests are now passing on Windows 64 bit and (I think) 32 bit using MSVC. Getting everything running on 64 bit windows is a real pain to work out, so I wrote instructions and included them in the installation docs.

Fixes #172, #365.
I think it should just be a matter of changing this line, maybe to ``if compiler=='unix':`` or something like that but hard to test without having a linux distribution handy.