follow up to matplotlib#6714

At request of fedora package maintainers.

closes matplotlib#6536

…dency-check

ENH: Added support for `mgs` to Ghostscript dependecy checker

DOC: explain behavior of notches beyond quartiles

TST: add test for CFF / OTF files

MNT: use _get_data_path is cbook

MNT: Use subprocess32 on python 2.7

When scaling the dash pattern by the linewidth do the scaling at artist
creation / value set time rather than at draw time.

closes matplotlib#6592
closes matplotlib#6588
closes matplotlib#6590
Closes matplotlib#6693
closes matplotlib#5430

…caling

FIX: refactor dash scaling

Second beta for matplotlib v2.0.0

- fixed bugs in scaling dash pattern by linewidth
- fixed over/under propagating in images
- back ported improved png API from master
- deprecate gtk, gdk, wx (not gtkagg, wxagg) backends
- tweaks to default font sizes
- ensure default ticker always has at least 2 ticks
- remove vendored version of `six`
- updated GUI icons
- many small bug fixes

Conflicts:
	lib/matplotlib/collections.py
	  import conflicts
	lib/matplotlib/lines.py
	   import conflicts
	lib/matplotlib/tests/test_coding_standards.py
	   adjacent lines were removed
	lib/matplotlib/tests/test_font_manager.py
	   multiple tests were added
	setupext.py
	   comments