Fixed some style issues. Added violinplot to boilerplate.py
Added comments for test cases referencing the origins.
Added silverman and scott tests.
implementations of the evaluate tests

Conflicts:
	lib/matplotlib/tests/test_mlab.py
Fixed kde for invalid bw_methods, misc test formatting.
Some course related tests were added. These are removed later.
Renamed vp_coverage baseline images, added bw_method paramater to violinplot and updated demo
Updated kde tests in test_mlab.py to reflect changes to imports in test_mlab.py
Fixed a syntax error in python 3 and fixed up some violinplot tests.
Fixed some style problems.
Removed course-related test from list of tests.
Fixed an issue in violinplot where the top end of violins would be truncated.
Updated test images and reran boilerplate.py
Refactored axes.violinplot into cbook.vp_stats (arranges violin plot data for drawing), axes.vplot (draws pre-arranged violin plot data), and axes.violinplot (uses cbook.vp_stats to draw violin plots via axes.vplot)