Make textures work with light

[KeyWeeUsr]

Based on #20

Examples fixed to work with light(shader)

• example2.py - testnurbs.obj & testnurbs.mtl were in some kind of weird/old format. I imported it to blender and re-exported without change. Now it works.
• trackball/main.py - fixed camera rotation via touch, camera clipping and edited, so that it looks good with lighting

Fixes in objloader.py

• if there is a value 0.000000, then the shader won't accept it for mixing for some strange reason, so a quick patch with making it default at 0.000001 does the thing
• include an "empty" texture, so that the shader can mix, but disable the texture immediately after including
• shorter path code

Edit .gitattributes to treat .mtl files as binary