Add Travis configuration

As discussed in #99. There are already tests that [pass](https://travis-ci.org/backspace/refugerestrooms/builds/22124960), though they aren’t the acceptance tests that I described in the other thread, which I can get started on in another branch.

I added a Travis badge to the readme, but it will show “unknown” because the original repository isn’t set up with Travis yet. If you want to merge in this pull request, follow Travis’s [getting started guide](http://docs.travis-ci.com/user/getting-started/), and once you enable it for the refugerestrooms repository, the build status will be displayed correctly on GitHub!

Here’s the build status for my branch: ![integrate-travis-ci branch build status](https://travis-ci.org/backspace/refugerestrooms.svg?branch=integrate-travis-ci)