Update image to Trusty and PostgreSQL 9.3

[Quantal is not supported anymore](http://fridge.ubuntu.com/2014/05/17/ubuntu-12-10-quantal-quetzal-end-of-life-reached-on-may-16-2014/) and PostgreSQL 9.1 is somewhat antique.

I've also fixed up the README a bit, though it could be more detailed.