Saucelabs support

This pull request is only so that we can do an internal code review. We will not get merge it, but send a pull request upstream.

@arunoda, we are adding Sause Labs support to travis-ci-meteor-packages. Would that be something you would be interested in merging in?
It's a node package since I mark it as a [node project](https://github.com/peerlibrary/travis-ci-meteor-packages/blob/master/.travis-sample.yml#L2). But you might can remove it and use a makefile.