matplotlib Code

Small optimization.

Add energy display in the same units as the potential

Add Schrodinger equation example, contributed by James Nagel <nagel@...>

tweaked cbook.dedent, inspired by Fernando's version

added config module, for testing a traited config system

Numpy has isfinite, unlike the old numerix

Some examples to go with the last commit.

Lots of sizing and layout tweaks. Support $\sqrt[3]{foo}. The line
meets up with the check mark rather clumsily on the Agg backends due
to rounding errors and lack of subpixel placement... will look into that.

Fix bug in pdf backend (numpy.inf not numpy.infinity)

Update information about mathtext improvements.