Should work across windows, mac and linux now

Added -Werror, and some -D CCflags as extraneous changes. Everything else is just modifying lib/flags based on detected OS. Couldn't test on windows but all 3 commands (make clean/install/uninstall) work just fine on osx.

I might suggest including the required library inside of your game for static linking so users don't have to download it and install themselves.