Building in windows under MSYS

[TomBPotochek]

I was able to compile and run this project in the master branch under msys mingw, but only after removing the trailing / from the include directory paths in the Makefile (and after almost banging my head against the wall).

Would this change break support on other platforms? Maybe this is just some weird bug in my pc setup but if it doesn't break other builds then they could be removed and automatically support windows builds.