fix the pyplot version of rc_context

[ivanov]

Before this, when using the rc_context dangling from pyplot, one would
get an AttributeError for __exit__, because plt.rc_context wasn't
actually returning anything before this change.

[ivanov]

even though this is a bugfix, it doesn't apply to v1.2.x, because pyplot didn't expose rc_context, it was only available from matplotlib proper.

[ivanov]

Travis error on Py2.6 because it couldn't satisfy the PIL requirement, so I think that's a dud. 2.7 and 3.2 are green

[pelson]

The fix is good. 👍 on that front.
I wonder if we need rc_context in pyplot though? It's fairly easy to get at with matplotlib.rc_context...

[ivanov]

plt.rc() and plt.rcdefaults() have been there since at least 2007 (git blame tells me that @efiring was the last to edit those lines then). So previously we could permanently change the rc params from plt, but not temporarily, and since now we have the handy contextmanager to do just that, it makes sense to expose it in the same place.

[pelson]

So previously we could permanently change the rc params from plt, but not temporarily, and since now we have the handy contextmanager to do just that, it makes sense to expose it in the same place.

I can't argue with that. 😉