Enabling Travis-CI builds

This enables jsUri to run builds upon push (including PR submissions) on [Travis CI](https://travis-ci.org/).  However, this also requires a change to the repo settings itself to add a Travis-CI service hook.

@derek-watson: Can you enable that service hook?

P.S. The "README.md" is all pissy about whitespace changes. Add a `?w=1`/`&w=1` to the URL to ignore whitespace in the diffs, i.e.: https://github.com/derek-watson/jsUri/pull/28/files?w=1