some flake8
Add a test for PalmImagePlugin.py
Ensure rowbytes is an integer (fix for Python 3)
Refactor and add two more tests
Merge branch 'master' into HEAD
Fix dispose calculations

- use correct dispose mode
- only apply the dispose on extent of the previous frame
Handle transparency between frames for animated GIFs

Show the previous frame for transparent pixels when the disposal method is 'do not dispose'.

This fixes issue 634.
only update the disposal_method if it not 'unspecified'
More tests for ImageFont.py
Add test image using ImageFont's default font
flake8 and fix path in __main__
More tests for ImageMath
flake8 ImageMath.py
Failing test for messed up P image on write only format
Skip known bad tests
Merge from master
Don't exclude Windows code
Merge pull request #776 from wiredfool/palm

Palm image test
Update CHANGES.rst [CI skip]
Document environment variable method for pip, #720 [ci skip]