matplotlib Code

Remove the "markup" kwarg and rcParam everywhere and replace it with
an automatic detection of math markup.

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

Removed mathtext2. Fix horizontal centering in mathtext. Put all
mathtext_examples on one plot.

Make LaTeX preview show things in displaymath mode, since that's what
we're trying to emulate.

Minor speed improvements from profiling. Fix kerning corruption issue when
"shrinking" characters.

Add support for \widehat and \widetilde

Add kwarg 'markup' for all text that allows the user to choose either
'plain' or 'tex' markup. A default may also be provided in the
rcParam 'text.markup'.
Minor bugfix to mathtext.py

Some examples to go with the last commit.

Merging mathtext changes into trunk.