re-added lines to make sure that `bottom` and `left` are not None in
the case of `log=True`.  If this is not done, there will be type
exceptions.

Issue #1882
simplified logic related to bottom=None and log in `bar`
Added support for providing 1 or 2 extra colours to the contour routines to easily specify the under and over colors.
qt4_editor formlayout now works with colour tuples
Fixed call to path.Path.contains_point from pnpoly. contains_point accepts a list as its first argument.
@efiring's suggestion.
Add a what's new entry for the WebAgg backend
Request a specific version of Gtk when using gi
Clean up text and links in screenshots page of user docs.
Tweak aesthetics of plots in screenshots page.

These changes also cleanup the code a bit, as described by MEP 12.
Add streamplot function to screenshots doc
fix pstoeps function in backend_ps.py
Added an api_changes entry for contour levels & colours with the extend keyword set.
Merge pull request #2033 from leejjoon/fix-pstoeps

fix pstoeps function in backend_ps.py
fix pstoeps function in backend_ps.py
Added the cleared method to Path, and updated the path module's documentation.
Made the Path created by cleared consistent with the actions that have taken place.
Fix missing ticks on inverted log axis
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.