Update Travis CI Settings

Using Postgresql with Travis CI doesn't work right out of the box.
According to the [docs](http://docs.travis-ci.com/user/postgresql/) you
must first configure the database with the `postgres` user and then make
sure your database.yml file matches up. Since I don't want to re-work my
local test environment to accommodate this flow, I am using a separate
database.yml file for Travis.