ENH: add PostgreSQL support for pandas.io.sql.get_schema
Simple changes to add PostgreSQL syntax to `pandas.io.sql.get_schema`. Added data type cases for `get_sqltype()` and a columns "flavor" for `get_schema()`. 

@adamgreenhall take a look at the master issue #4163, also pls hook up travis (see contributing.md)
 Thanks @hayd. Will setup Travis and open a pull request against the `sql` branch.
 Fantastic! Please ping me when you do. (I've some alchemy work on it pending..)
 @hayd: new PR now up at: https://github.com/pydata/pandas/pull/4680
