In introduces you to using TravisCI to provide continuous integration services for your project (externally). Continuous integration is a way to provide "quality control" of your code, making it easier to run testing, check syntax and more, small pieces at a time.
Travis CI in fact works by tying itself to a particular project on Github, and by triggering a new build every time new commits are available on the chosen branch (master, usually). Your build shows up on the main page along with all the other projects in the newsfeed, so try to maintain it green. :) Travis CI adds this other aspect to Github's social coding.
He talks a bit about how it works - builds running on VMs, some with advanced tools like Selenium - and includes an example based off a simple travis.yml file defining a script to run pre-build. He also points out a special caveat about databases - they support things like MySQL, Sqlite, MongoDB and CouchDB, but you'll have to generate them from scratch every time, sample data and all.