Fix Windows Build

[rgoulter]

Commits since 2013 had broken the build for Windows.

e.g. use of namespaced geometry::Polygon as Polygon conflicts with a function (macro?) from windows.h. Also references to SOIL.h and other things like that.

[rgoulter]

Fixed by #18.

For what it's worth:

• AppVeyor build would've caught this much earlier.
• I don't find the "C++ run time" environment on Windows to be super obvious.
  • If all the libraries/dependencies were statically linked, then this wouldn't be much of an issue.
  • There doesn't seem to be an easy way to magically copy the appropriate .dlls. (Nor, apparently, does Windows have a filename convention for static vs shared library).
  • It's possible for the program to be built, but the PATH to not have the appropriate DLLs. Which means that when trying to run the program, it can't find the DLLs.