matplotlib Code

Lots more work on making examples work. Details, details, details...

Simplified sharing axes again.
Plowing through -- making more examples work.
First pass at updating collections (LineCollection mostly works)

Lots of progress on Polar transform refactoring. Added point_in_path algorithm.

Minor speed improvements in new transformations.

First baby step in getting arbitrary non-linear transformations into
the pipeline.

Lots of minor fixes

Removed transforms on the C++ side -- removed many methods that depend
on it in backend_agg in preparation for path generalization.
Lots of general renaming...

New milestone -- resizing figure window works. shared_axis_demo.py
works. (Uses callbacks to track changes between axes's).

Minor changes -- committing so I can merge again.

Second pass, using a stateful transform tree.