Cleanup comments from example
Allow dropping file (.png) onto demo to change skin texture
Fix body front texture left/right orientation

You can tell because with MC's steve skin, the shirt is tucked in on the
left, not the right.
Add arm rotation uniform. Closes GH-5
Fix stretched inner textures (not noticed before since they were obscured by the arms)
Fix arm rotation axis
Smooth arm swing movement in demo
Add leg rotation uniforms, split left/right arms. Closes GH-5
Fix inner left leg texture
Change demo texture to use @substack's skin

From https://github.com/substack/voxel-player/blob/master/example/static/substack.png

This skin is better for testing since it includes outlines around
the edges, and also a texture for the body lower face (unlike viking.png).
Add documentation
Add link to demo