Fix compatibility with Python 2.6
Use setuptools' setup function if available
Setup Travis
Add few matrix33 docstrings
Implement matrix44.create_perspective_projection_matrix
Add build status indicator to readme
Fix perspective projection matrix
Add sections to index page.
Reword contributors section.
Add requirements.txt to requirements-dev.txt.

Some webhook sites expect this (readthedocs).
Update Pyrr doc url
Fix texinfo description.
Fix up docstrings for matrix33, matrix44, matrix.
Add encoding string
Update docstrings to use sphinx format.

Add a number of comments.
Fix a number of incorrect comments, the worst of which
were stating that modifications were occuring in-place.
This is NEVER true in Pyrr.
Remove unused import.
Replace plane maths with A,B,C,D representation.

Update Plane.py docstrings.
Update geometric_tests.
Update unit tests.
Fix test using assertEqual on a boolean.
Update docstrings
Replace sphere with vector4.

Sphere is now vec4 with position as X,Y,Z
and radius as W.