Add a what's new entry for the WebAgg backend
Merge pull request #2011 from pelson/api_changes_sketch

Added the "cleared" method to Path, and updated the path module's documentation.
Merge pull request #2002 from pelson/contour_levels_with_colors

Added support for providing 1 or 2 extra colours to the contour routines to easily specify the under and over colors.
Merge pull request #2028 from mdboom/additional-whats-new-1-3

Add a what's new entry for the WebAgg backend
Added a coding_standards test module. Currently checks PEP8 compliance on all files except those explicitly excluded.
Added some of the PEP8 guidelines to ignore in the coding standards test.
Fixed failing PEP8 test.
PEP8 test only on python2. 2to3 produces non pep8 compliant code.
Fixed tests after rebase.