data file for plotprecip.py example.
added extra colormaps.
add script to plot basemap colormaps.
extra colormaps for basemap (most from Generic Mapping Tools)
fixed a filling rule bug in agg
Add L-system example contributed by Stefan van der Walt
update requirements
use numpy.random instead of numerix
don't 'from pylab import *'
fix typos that prevented script from working
