Merge pull request #10 from infinityb/master

~Octree~
Add some form of fresnel.
Make Lucy look more similar to Lucy pre-fresnel.
Fix sphere test scene.

Bad sphere material after fresnel update.
Fix refraction recursion not terminating right.

~oops~
Tone down floor specular on Sponza.
Fix octree not working for scenes with few objects.
Update license file.
Add Sibenik scene.
Octree performance improvements