Fixed failing bbox_inches='tight' case when a contour collection is empty.
Fixed background colour of PNGs saved with a non-zero opacity.
Make the travis output slightly quieter, particularly when installing dependencies.  Add Python 3.3 to the tests.
Merge pull request #1965 from mdboom/simplify-travis

Make the travis output quieter on v1.2.x
Bug if MPLCONFIGDIRS is set
Switch agg backend to use pixfmt_rgba32_plain instead of pixfmt_rgba32, which fixes a problem with alpha-blending partially transparent backgrounds.
Merge pull request #1868 from pelson/alpha_background

Fixed background colour of PNGs saved with a non-zero opacity.
Fix position of rotated text in Agg backend
Merge pull request #1968 from mdboom/rotated_text

Rotated text element misalignment in Agg
Merge pull request #1929 from pelson/bbox_inches_contour_problem

Fixed failing bbox_inches='tight' case when a contour collection is empty
Update pngsuite.png test image
Fixed failing bbox_inches='tight' case when a contour collection is empty.

Conflicts:
	lib/matplotlib/tests/test_collections.py
SubplotBase._make_twin_axes always creates a new subplot instance. Fixes #1957.
Fixes imsave so it does not flatten alpha-channel data (and updated test to match)
Skip over zero-length subpaths.  Calculate for each subpath and then "or" those results together.
Fix #1973: offset_position == 'data' is not respected by point_in_path_collection
Escape XML comments correctly when writing out SVG.  Turns '--' into '- -'
Merge pull request #1967 from mdboom/svg-comment-escape

svg double hyphen in plot title --
Merge pull request #1956 from Westacular/imsave_alpha

Imsave now preserves the alpha channel.
Add a test for #1787