Save time zones in postgres driver

The current format doesn't save the time stamp, which leads to undefined behavior when updating a TIMESTAMP WITH TIME ZONE column.
Merge pull request #28 from maxhawkins/patch-1

Save time zones in postgres driver
Adding specific host for testing against local virtual machine.
Merge branch 'experimental'
Adding tests for ordering by function. Will help closing #32.
Adding order by function on SQLite, PostgreSQL and MySQL adapters (#32).
PostgreSQL: Adding support for nullable fields. Issue: #26.
MySQL: Adding support for nullable fields. Issue: #26.
SQLite: Adding support for nullable fields. Issue: #26.
Adding test table for testing column cases.
sqlgen: Adding GROUP BY clause support.
sqlgen: Removing unrequired field.
Adding interface for grouping results by column (Group()).
PostgreSQL: Adding support for db.Result.Group().
MySQL: Adding support for db.Result.Group().
Fixing comment formatting for db.Result.Group().
SQLite: Adding support for db.Result.Group().
QL: Adding support for db.Result.Group().
MongoDB: Adding placeholders for group by support. Currently not implemented.
Adding precedence over column name to field name mapping. Closing #27.