Configure travis.ci to run integration tests

I have being using travis.ci with bunch of other projects and it's being great to be able too see status of test run in the pull requests regardless of weather you submit a change or do a review. It would be really useful to have this for clojurescript too.

Tests do work on my fork right now:
https://travis-ci.org/Gozala/clojurescript

In addition to pulling this change github hook needs to be enabled (before the pull) to trigger tests runs on pull requests and pushes. Details on this can be found here:

http://about.travis-ci.org/docs/user/how-to-setup-and-trigger-the-hook-manually/