Remove ipython doc dependency

[mirca]

Since #14 got merged, it looks like docs do not dependent on ipython anymore.
So, hopefully closes #16.

cc @nocturnalastro @bsipocz

[bsipocz]

@mirca - Looks good, though I wonder why you've skipped the doctest for some of the snippet lines?

[mirca]

@bsipocz Those lines which are skipped are tested under the plot directives. I've skipped some so that I don't need to repeat the whole code under plot. :)

[bsipocz]

I mentioned it only as leaving them untested gives a chance to diverge in future.
That said I have to admit that there are packages without running doctest on the narrative docs that I yet have to fix, figure out how to do better.

[mirca]

@nocturnalastro are you happy with these changes? ;)

[nocturnalastro]

@mirca, sorry I hadn't looked before.
Looks fine, as @bsipocz said we'll have to keep an eye on changes made to the docs to make sure that the plot and snippets are the same so we don't have to worry about testing the snippets.

[mirca]

@nocturnalastro sure!