This patch allows a JPEG image to be saved with a specific qtables
value (in dictionary format).

Previously, this would throw a TypeError when checking if the qtables
value was actually a preset. By adding an isStringType check, we can
avoid this error.
Merge from master
Merge branch 'master' into jpeg_qtables
Fixed JPEG qtables test
Additional jpeg qtables tests
Added docs for JPEG qtables and subsampling
flake8 on morphology changes
Update a docstring [CI skip]
Make test runnable on its own
Match real palette format in ImagePalette.save()
Update ImagePalette.py

According to __init__, using `len(self.mode)` might be better. Tested on my machine.
Merge pull request #714 from wiredfool/jpeg_qtables

JPEG qtables
Update
Merge pull request #716 from hugovk/morph_flake8

Flake8 on morphology changes
Added roundtrip test for ImagePalette.save
Merge pull request #719 from wiredfool/imagepalette

Tests for Imagepalette.save()
Updated Changes.rst [ci skip]
Multithreaded build
Limit buildprocs on travis
Merge pull request #721 from wiredfool/multiprocessing_build

Multiprocessing build