Fix for rich comparison and add test for vec3 file

As __cmp__ no longer in Python 3 need to use functools.total_ordering which is in 2.7 and 3.*
  https://docs.python.org/2/library/functools.html#functools.total_ordering
  https://docs.python.org/3/library/functools.html#functools.total_ordering
  Define __eq__ and __lt__ and others are created automatically

Add unittest style for file vec3.py
This example shows that the code was probably never used much in real life. I'm not sure if we should invest a lot of effort into the Vec3 class.