matplotlib Code

[2687673] Add abs() to delta check in Mollweide projection.

[2687673] Fix problems with Mollweide projection, enable it, and add to geo_demo.py

Spine is now derived from Patch

make default argument to Axes.get_xaxis_transform() not raise error

I made this a separate commit from the previous one because it may be
useful to see the errors that arise if get_xaxis_transform() or
get_yaxis_transform() are called with no arguments. This would allow
one to figure out which code paths are calling these methods and fix
them if needed rather than silently partially succeeding.

Arbitrary spine placement

Fix degree display in geographic transforms, also.

Fix rectangular polar axes patch.

fix numpy, ma imports in geo.py

Fix title placement in polar plots. Remove broken auto layout code.

Fig dpi-changing-related bug where tick label padding was not updating
(Thanks Eric Firing for finding this).