Manage official postgres apt repo

Previously we hadn't supported using the official PostgreSQL repos for deb-based
packaging. This commit fixes that by introducing the management of the apt
repositories on the host as required, and using the correct package and service
name.

Signed-off-by: Ken Barber <ken@bob.sh>
Fix examples for specifying usage of official postgresql repos

This changes the wording and name of the example for using
yum|apt.postgresql.org as the source of your packages.

Signed-off-by: Ken Barber <ken@bob.sh>
Merge pull request #75 from cprice-puppet/kbarber-ticket/master/manage_postgres_apt_repo

Kbarber ticket/master/manage postgres apt repo