class/function summary tables only show first line of docstrings - #231

I put this question on stackoverflow, and it looks like there is an answer that could be useful: http://stackoverflow.com/questions/10718846/use-first-paragraph-instead-of-first-line-in-sphinx-autosummary

However, this might require that we bundle a modified autosummary (or we can submit it as a patch to sphinx).

It turned out to be possible to just copy over the relevant part of Autosummary to Automodsumm and fix it there. So these commits now fix the problem (using the suggestion in the response to the question @astrofrog asked on stackoverflow).

@taldcroft - note that I also had to slightly adjust some of the astropy.io.ascii classes because they were doing weird things in the summary tables. Let me know if any of these (small) changes should be altered.

And see https://bitbucket.org/birkenfeld/sphinx/issue/943/autosummary-doesnt-always-get-first - that fixes the issue in sphinx, so if it is adopted we could alter Automodsumm to only include this stuff if the sphinx version is too old.

@eteq - No problem with the io.ascii doc changes.

I'll go ahead and merge this, and issue a second PR that address the issue I was waiting on fixing.