Made ordinary and fast ASCII readers store comments in Table .meta

This is meant to address #3136.
That's me fault. ;-)
Just trying not to favour any individual name in the documentation ;-)

But I agree that three lines of comments are enough.

On 12/22/2014 02:05 PM, Tom Aldcroft wrote:
>
> In docs/io/ascii/read.rst
> <https://github.com/astropy/astropy/pull/3222#discussion-diff-22183558>:
>
> > +^^^^^^^^^^^^^^^^^^^^^
> > +
> > +Any comment lines detected during reading are inserted into the output table
> > +via the ``comment_lines`` key in the table's ``.meta`` dictionary. For example::
> > +
> > + >>> data = ascii.read(['# comment 1', '# comment 2', 'a b c', '# comment 3', '1 2 3'])
> > + >>> print(data.meta['comment_lines'])  # doctest: +SKIP
> > + ['comment 1', 'comment 2', 'comment 3']
> > +
> > +While :mod:`astropy.io.ascii` will not do any post-processing on comment lines,
> > +custom post-processing can be accomplished by re-reading with the metadata line
> > +comments. One example is given below, where comments are of the form "# KEY = VALUE"::
> > +
> > + >>> table='''# TELESCOPE = 30 inch
> > + ...          # TARGET = PV Ceph
> > + ...          # OBSERVER = me
>
> In the interest of space this |OBSERVER = me| could be cut without any
> sacrifice.
>
> —
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> <https://github.com/astropy/astropy/pull/3222/files#r22183558>.
>