ENH/SQL: support writing timestamps with timezone in to_sql
This currently works a bit for datetime values in the index (not in the columns, reason for this is that is then are object columns: #9085). 
I say 'a bit', as it does give a 'timestamp with time zone' type (example for postgresql), but it is the time localized in your local timezone (I suppose because this is the way numpy works on input/output of datetimes).

In any case, also the code here (https://github.com/pydata/pandas/blob/v0.15.2/pandas/io/sql.py#L916) is not working (as columns never have a `tzinfo` attribute), and there are also no tests for this.

So in practice, timezones are not yet supported.
