Failing tests.
Fixes bug where linestyle always appears solid if linewidth is large enough
Fixes bug where if alpha is set and edgecolor='none', edges would still be rendered as black.

Also fixes test case result that hit this bug
Changes backends to support of independent face and edge alphas

Specifically, alters the base, AGG, PDF, PGF, SVG, Cairo, and Mac OS X
backends to better enable the use of RGBA color values for both fills
and edges. An explicit alpha attribute, if set, will override the
alpha channels of the color values.

Updates test results, which are now what would be expected.

Also fixes a couple bugs with handling of linestyles.
Add additional patch tests.
Added documentation of patch/alpha changes.
Another documentation update
Documenting the isRGB -> isRGBA change to API
Merge pull request #1954 from Westacular/alpha-patch

Supporting different alphas for face and edge colours