SkyCircleRegion matplotlib plot issue

In #74 @joleroi added [docs/plot_compound.py](https://github.com/astropy/regions/blob/master/docs/plot_compound.py) which generates this plot:
http://astropy-regions.readthedocs.io/en/latest//plot_compound.png

As discussed in #74, there is an issue, the region is not drawn correctly.
To @joleroi and me the script looks OK, so we don't know what's wrong.

@astrofrog or @larrybradley or anyone - if you could have a look, that would be great!

Start with docs/plot_compound.py and run it to reproduce the incorrect region plot linked in the issue. Compare the generated plot with the intended region, then identify the cause and verify that the corrected plot draws the region correctly.

Written by the indexing model from the issue text.