`afm.get_fontconfig_fonts` returns a list of paths and does not check for existence

`afm.get_fontconfig_fonts` used to return a set of paths encoded as a

``{key: 1, ...}`` dict, and checked for the existence of the paths. It now

returns a list and dropped the existence check, as the same check is performed

by the caller (`afm.findSystemFonts`) as well.

`bar` now returns rectangles of negative height or width if the corresponding input is negative

`plt.bar` used to normalize the coordinates of the rectangles that it created,

to keep their height and width positives, even if the corresponding input was

negative. This normalization has been removed to permit a simpler computation

of the correct `sticky_edges` to use.

Do not clip line width when scaling dashes

The algorithm to scale dashes was changed to no longer clip the

scaling factor: the dash patterns now continue to shrink at thin line widths.

If the line width is smaller than the effective pixel size, this may result in

dashed lines turning into solid gray-ish lines. This also required slightly

tweaking the default patterns for '--', ':', and '.-' so that with the default

line width the final patterns would not change.

There is no way to restore the old behavior.

Deprecate 'Vega' color maps

The "Vega" colormaps are deprecated in Matplotlib 2.0.1 and will be

removed in Matplotlib 2.2. Use the "tab" colormaps instead: "tab10",

"tab20", "tab20b", "tab20c".