Can't drag zoom on a polar plot. Finessing Agg drawing quality a little bit.
Fix polar plot title so it doesn't clash with 90 degree value.
Removed unused imports.
added convolve workbook
added more convolution figs
added convolution demo figs
added some figs for convolution example
Added BboxTransformFrom/To for more efficient bounding box transforms.
More coverage. Add draw_path_collection to SVG.
added quicksort example
