Postgresql database support and pin requests

This add postgresql support for grunt.

And because of an upstream bug[1] in python-keystoneclient, we need to
pin to version 2.3.0.

[1] https://bugs.launchpad.net/python-keystoneclient/+bug/1363179

Change-Id: I16dc2452ad3fce88d02ab1c4eb0b175dcbddd592
Signed-off-by: Paul Belanger <paul.belanger@polybeacon.com>