Xfailing because the Dev Derby will be on hiatus from August to October

The Dev Derby will be on hiatus from August to October while they work on revamping the contest series. And some elements are missing from the page through this time (judges tabs for example)
https://developer.mozilla.org/en-US/demos/devderby
https://hacks.mozilla.org/2013/06/announcing-an-administrative-change-to-the-dev-derby/