SwiftGL is now 100% pure Swift

Turns out it's possible to make an OpenGL loader entirely in Swift. So
SwiftGL is now a complete OpenGL loader without any dependencies. Over
30,000 lines of 100% pure Swift. Every OpenGL command and extension that's
in the spec as of today is supported.

I tested SwiftGL on OS X 10.11 and Ubuntu 14. It should work on all
versions of OS X and Linux that Swift runs on.

We still need a GL math library and window manager for the open source
Swift. Please let me know if you want to work on either of these.

-david