Docstring for ArtistAnimation is incorrect

[typograph]

The docstring for the ArtistAnimation class mentions frame_info, although the argument to the constructor is called artists. I would suggest changing the argument name back to frame_info, as artists makes one think this should be a simple collection.

[dopplershift]

Changing the name of the parameter would technically be an API break, since someone could be passing it as a keyword argument. I'd be happy to take a Pull Request to fix the docstring and change frame_info to *artists* (asterisks should be there as well since it's documenting the method parameter).