Updates!

zlib is now required and imported by the framework, and will be used in some module, I'm sure.
SEngine is now a little bit more organized when it comes to library loading; I might import some of the magic from lcore to get it working out a little bit better, though. This could mean an additional dependency.
Both the OpenGL and GLFW3 bindings are a little cleaner, and SEngine no longer imports their namespaces into the global namespace by default.
main.lua now contains a demo, and sengine/init.lua actually contains initialization code!

graphics/window.lua is starting to contain a wrapper over the GLFW Window object