matplotlib Code

Added step plot based on patch by Manuel Metz

Removed last vestiges of old pcolor, scatter, quiver versions.

minor modernization

added xcorr and acorr plot functions

Moved pylab._shift_string() to cbook.dedent() to facilitate its use

added tims spectral patch

Replace old spy and spy2 with new spy (briefly called spy3)

Removed body of scatter_classic, leaving exception-raising stub.

Remove pcolor_classic

added broken barh