Accept either a w coordinate component or an RGB color for vertices

[SwishSwushPow]

This fixes an issue where it was not possible to parse obj files that provide a w-component with their vertex coordinates. Vertices can now come with a w-component OR RGB colors. I went with this route because of the information that can be found on the Wavefront .obj Wikipedia page.

A vertex is specified via a line starting with the letter v. That is followed by (x,y,z[,w]) coordinates. W is optional and defaults to 1.0. W scales the point. The point (x,y,z,w) corresponds to the point (x/w,y/w,z/w). A right-hand coordinate system is used to specify the coordinate locations. Some applications support vertex colors, by putting red, green and blue values after x y and z (this precludes specifying w). The color values range from 0 to 1.

Also added new tests for these cases.