Fixed failing bbox_inches='tight' case when a contour collection is empty.
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
Fixes imsave so it does not flatten alpha-channel data (and updated test to match)
Merge pull request #1956 from Westacular/imsave_alpha

Imsave now preserves the alpha channel.
Merge remote-tracking branch 'upstream/v1.2.x'

Conflicts:
	.travis.yml
	lib/matplotlib/tests/baseline_images/test_png/pngsuite.png
	lib/matplotlib/tests/test_axes.py
Replace usage of Lena image in the gallery.

Note that lena.npy was created in PR #1924 before I realized matplotlib could read png images without PIL. That file wasn't used anywhere else, so I remove it here.
Fix `backend_driver.py`

A couple of files were removed in PR #1918, but were accidentally re-added to `backend_driver.py` by PR #1924.
Fix Travis config
Merge pull request #1977 from tonysyu/fix-backend_driver

Fix `backend_driver.py`
Merge pull request #1976 from tonysyu/replace-lena-in-gallery

Replace usage of Lena image in the gallery.
Allow local libpng copy
Change message when libpng pkg-config lookup fails
Go back to one ghostscript process per test
Fix some test images that weren't being run on Travis before
Run tests in parallel on Travis and in tox
Include all test files
Make the test function name match so that they can be pickled through multiprocessing
Don't call "show" from a test
Fix typo so correct gs executable will be run