enable automated testing on travis-ci.org

Any package with Tinytest set up shouldn't pass on the ability to have automated tests be run for every commit and pull request! This makes it a lot easier to see when something has broken, as well as notifying if pull requests are working or not (at a minimum level.) It also adds a cool little build badge for the current status.

This package sets up @arunoda's https://github.com/arunoda/travis-ci-meteor-packages for this repo.

Before merging, either @cmather or @tmeasday will need to go to https://travis-ci.org/EventedMind/iron-router/ and turn on automated testing for this repository. For more information see the instructions in the readme for @arunoda's repo.