Update Travis CI configuration to run only on master branch against the latest mozilla-central nightly build
Skip email tests if account details are not present in test variables
Use SkipTest from Marionette instead of unittest
Switching to Twitter, as Lanyrd app is not appearing in results on B2G desktop
Wait for the browser tab list to be shown/hidden fully
Changing the keyboard language will still not pass on desktop
Merge pull request #1056 from davehunt/travis-fixes

Travis CI fixes