Allow tests to be run in Sauce Labs using `RUN_IN_SAUCE_LABS`
Do not encrypt Sauce Labs username/access key

This allows tests to run from foreign PRs, re. http://docs.travis-ci.com/user/pull-requests/\#Security-Restrictions-when-testing-Pull-Requests
Add docs on how to run tests in Sauce Labs

[ci skip]
Merge pull request #105 from guardian/oja-sauce-connect

Allow PRs to run tests and document how to run tests in Sauce Labs locally