Different alphas for lines and fills.

I saw an interesting [question on Stackoverflow](http://stackoverflow.com/questions/15928539/matplotlib-how-to-make-the-marker-face-color-transparent-without-making-the-li/15936516#15936516) the other day for which I found it was possible to supply an RGBA for both face and edge colors separately. I'm guessing this isn't tested, so thought I would add a comprehensive test, **unfortunately the test results are wrong (so don't merge this)**.

Am I doing something silly in the test?