Define provision:14_04 task.

This can be used as a hook to do Ubuntu 14.04-specific provisioning steps.

Note that provision still defaults to 12.04. This means that provision and
provision:12_04 can be used interchangeably.
Add 14.04-specific aptitude steps.

This prepares the apt system for installing PostgreSQL-related packages. The
PostgreSQL apt repository for 14.04 requires special setup.
Release 0.10.0