Added check in autoscale_None for completely masked pcolor plots.
Only set `use_2to3` on Python 3.
fixes issue with using transparency for the figure patch and
being able to see shadows of previous draws underneath.

see: http://stackoverflow.com/questions/18944561/matplotlib-pyqt4-transparent-figure

Added some documentation to `paintEvent`
Merge pull request #2449 from tacaswell/qt4_clear_before_draw

Qt4 clear before draw
Merge pull request #2446 from mdboom/old-distribute

Don't set use_2to3 unless we have to.
Updated gitignore to exclude build files from the examples.
Merge pull request #2455 from pelson/gitignore_update

Gitignore update
Hide the .cached member of Text so it doesn't get documented.
Add API change note.
Merge pull request #2457 from mdboom/private-members

Privatize Text.cached
Fix building of tarball
Fix ConnectionPatch to correctly account coordsB argument. Closes #2377.
Add What's new entries for 1.3.1
Python3 handling of None > None.
Merge pull request #2336 from pelson/completely_masked

Added check in autoscale_None for completely masked pcolor plots.
Merge remote-tracking branch 'upstream/v1.2.x' into v1.3.x

Conflicts:
	lib/matplotlib/tests/test_colors.py
Merge remote-tracking branch 'upstream/v1.3.x'

Conflicts:
	lib/matplotlib/text.py
	setup.py