Disable unnecessary GLFW build steps.
Added placeholder code for a fixed-timestep update
Added a model of the Sponza cathedral.

Copyright Marko Dabrovic. Obtained from:
http://hdri.cgtechniques.com/~sponza/files/
Exported the Sponza model as COLLADA format.

Performed using Blender, importing and then immediately exporting.
Exported Sponza as a PowerVR GeoPOD format file.

See http://goo.gl/uhyc8Z for more.