matplotlib Code

Clean up cycles to prevent memory leak.

Specify numpy requirement in README

removed possible backend ambiguity from memleak_gui.py

fix small problems left by rc refactoring

Fix grayscale specification in demo

updated CHANGELOG for memleak-related commits

More command-line options for memleak_gui.py

Patch by Mike Droettboom, tracker 1745408, fix mem leak in wx
https://sourceforge.net/tracker/index.php?func=detail&aid=1745408&group_id=80706&atid=560722

tiny fix to example code

fix some C compilation warnings