Generate API docs for astroquery.utils and astroquery.query

While working on #303 I noticed that e.g. `TableList` currently is mentioned to the end-user in the Vizier docs, but no API docs are generated for everything in `astroquery.utils` (see [here](http://astroquery.readthedocs.org/en/latest/search.html?q=tablelist&check_keywords=yes&area=default))

@keflavich What do you think about adding a new page to the docs for `astroquery.utils` and generate API docs for (at least some) of the methods there?
(It could be a bit hidden from the end-user docs, i.e. be part of the developer documentation if you consider this astroquery-internal implementation details, but I think it would still be useful to have.)