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
It looks like this fails if `names` isn't specified.  Should we just accept a `dtype` kwarg?  I don't remember the original reasoning behind writing this the way I did, so I might be forgetting something.