I believe Ubuntu 16.04 comes with PostgreSQL 9.5. Thats good for a start, but it is a matter of time before you have the need of a PostgreSQL 9.6 cluster. For me it was to import a PG backup from Heroku.
The procedure couldn't have been any easier and is described below. If you are interested in upgrading your old cluster to 9.6 afterwards, you may be interested in this.