Parse colors from vertex lines

[demkom58]

In some models, their colors are in the vertex lines, currently they are ignored.
I propose to add a reading of colors from such models.

Also I attached the test model:
some_model.zip

[Twinklebear]

This could be a useful feature to have, we can put it in to tobj. For rendering something like DTI tractography or other stuff this could be pretty handy