Install Sphinx extensions

[mdboom]

For what seems like a long time now, but matplotlib and IPython have both included ipython_console_highlighting.py and ipython_directive.py. (I think I wrote the former and John Hunter wrote the latter, originally).

Over time, these extensions have diverged. I think the IPython ones are better maintained as they actually track changes to IPython etc., and logically, I think these belong in IPython and not in matplotlib.

Unfortunately for third-party users of these packages, IPython does not install the sphinx extensions, but merely keeps them in the source tree. This has encouraged a lot of people to rely on the copies in matplotlib (which are installed). Any chance IPython could install them, too, then we could properly deprecate the copies in matplotlib?

[minrk]

I can't think of a reason that we shouldn't be doing that. Move them to IPython.sphinxext?

[mdboom]

EDIT: I overstated the case by accidentally comparing the wrong branches -- there don't seem to be any meaningful differences between the files in matplotlib and IPython. My thesis still stands (I think) that these more logically should live in IPython.