Fix bug in Line2D from last commit: restore full recache in unit chane callback
Line2D: simplify set_data functionality; recache only a coord. that was set.
fix whitespace, one docstring in lines.py
pyplot.spy should set current image only if it is making an image
Fix cmap data for gist_earth_r, etc.
Add docs for new features in mathtext
zorder support in figure: use same sort idiom as in axes
spines and ticks: implement smart bounds
spines: attempt to fix initial placement bug
spines: limit range in example
