Add Postgres specific PDO Adapter.
 - Supports placing migration table in a specific schema.
 - Adds timestamp to migration table.
Class is aware and checks for SCHEMA (uses public as default) but did not correctly check and create missing schema if not public.
Updated createSchema in SqlPgsql to accomodate the creation of a postgres scheme, i.e. 'CREATE SCHEMA schema-name'.
Merge pull request #69 from bgdevlab/feature/postgresSpecificPDO

Add Postgres specific PDO Adapter.