Fix issue with Sphinx 1.3.4

[jenshnielsen]

Fixes #5869 by rewriting the offending doc string as numpy doc

I also updated .travis.yaml. This originally started with the aim to ensure that the latest version of Sphinx and other dependencies is always installed by only installing Numpy and Pandas from the wheel house. (The wheel house requires manually rebuilding the wheel when a new version is released to pypi and was thus using an older version of Sphinx) The speed benefits are limited since other packages than numpy and pandas are fast to install and we now have the pip wheel cache on Travis anyway.

I took the opportunity to refactor the Travis config a bit more to collect all the pip installs one place and group relevant sections.

[jenshnielsen]

Looks like there is another issue with Sphinx 1.3.4 I will take a look tomorrow

Warning, treated as error:
['find_tex_file(filename, format=None)', ':module: matplotlib.dviread', '', '', '', 'Call :program:`kpsewhich` to find a file in the texmf tree. If', '*format* is not None, it is used as the value for the', ':option:`--format` option.', '', 'Apparently most existing TeX distributions on Unix-like systems', 'use kpathsea. I hear MikTeX (a popular distribution on Windows)', "doesn't use kpathsea, so what do we do? (TODO)", '', '.. seealso::', '', '  `Kpathsea documentation <http://www.tug.org/kpathsea/>`_', '    The library that :program:`kpsewhich` is part of.']:3: WARNING: unknown option: --format

[jenshnielsen]

It looks like that was as simple as removing the :option: key

[jenshnielsen]

I think the docs changes should be backported to 1.5.2 but the changes to Travis might not be wort it to backport

[jenshnielsen]

BTW it would be good to convert the rest of that file to numpydoc/napoleon too

[jenshnielsen]

There seems to be an issue with downloading the Cursive font from Googles github account. I should fix that before merging

[jenshnielsen]

Looks like the google fonts are back on github so this is ready for review

[jenshnielsen]

Sphinx 1.3.5 has been released with a fix for the regex issue so we don't strictly need 0ccce1b anymore but it's still an improvement. We do need 7f37443 to have it build cleanly with 1.3.5 thou

I am happy to separate out the travis changes if that makes more sense?

[tacaswell]

I will cherry pick this back but discard the travis changes

[tacaswell]

backported to 1.5.x as b7dfa4f