matplotlib Code

Fix \sqrt (broken when I made the parser more strict).

Fix a buglet affecting getp: if a numpy object has shape==(),
you cannot take its length.

rcdefaults working with mplconfig

Make rcParams.update(rcParamsDefault) when new traited config is
switched on.

add an update method to rcParamsWrapper

Run a simple sanity check to avoid attempting to parse non-AFM files as AFM.

Fix message about wxAgg version requirement.

Fix the parser so it doesn't silently fail. Speed up by using
pyparsing's packrat feature.

Making parser more robust -- will only accept valid symbol names.
(Re-)adding \hspace{ } command.

Fix docstring