matplotlib Code

First commit of code to embed fonts as paths in SVG files.

Add TTF subsetting to backend_pdf.py.

First pass of Type 3 font subsetting for Postscript backend. Made
ttconv code exception and threadsafe. Added subsetting.

Easy specification of default output format for cairo backend

Support for maskedarray alternative to ma

fixed a line collection rounding bug in agg that caused strange bugs when path lengths were 0

Use 'dashed' | 'solid' to specify contour negative linestyle

add unicode latex support

added the ability to insert arbitrary statements into
the latex preamble to customize usetex output.

some more units refactoring