Add sauce connect tunnel identifiers from travis ci
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/