into(sql, *) with better datetime support

changes and tests to support into(sql, *) where the source is
a pd.DataFrame, numpy array or dynd array, bcolz.ctable, or csv

If the source has a datetime with a timezone, make use of
sqlalchemy DateTime with timezone support

This also helps with operations of the form into(*, sql) where
the sql table has datetimes with time zone
> Your concern is that specifying a datetime with a timezone in the datashape reduces our testing in this area, right?
Yes

Your reasoning makes sense to me given the way things work now.  I'd still be more comfortable if we explicitly tested typical behavior.