Rename bug suggestion tab to Failure summary (1030678)

This work addresses Bugzilla bug [1030678](https://bugzilla.mozilla.org/show_bug.cgi?id=1030678). In brief:

* all code I could find related to the Bug suggestions panel has been converted to 'Failure summary'
* dist/ has been manually updated since it doesn't appear to be part of the grunt build process
* one css class `bug-suggestions` has been retired, since it appeared to be unused in the repo

I've tested it pretty extensively checking against passed and failed jobs, confirming the failure messages are present, but I am a newbie to treeherder (along with everything else) so it's entirely possible I've missed stuff.

Tested on Windows:
FF Release **30.0**
Chrome Latest Release **35.0.1916.153 m**