Add support for sauce connect

Adds support for using sauce connect when testing with sauce labs
instead of using local tunnel. Will utilize TRAVIS_JOB_NUMBER as the
tunnel identifier if running within travis-ci.

See:
http://docs.travis-ci.com/user/sauce-connect/#Setting-up-Sauce-Connect
and https://docs.saucelabs.com/reference/sauce-connect/
This code could use a comment saying what it is suppose to do.