Add remote top failures(#68)

This adds support for Top Failures for the remote branch.

We've missed this since we broke up the former Functional testrun into Functional and Remote.
It is hard to track the severity of Remote failures without this Top page.

This is basically a clone of the Functional Top Failures functionality.
See it in action:
http://mozmill-sandbox.blargon7.com/#/remote/top?branch=All&platform=All&from=2013-12-31&to=2014-01-07
http://mozmill-sandbox.blargon7.com/#/remote/failure?branch=29.0&platform=Mac&from=2013-12-31&to=2014-01-07&test=%2FrestartTests%2FtestAddons_installFromFTP%2Ftest1.js&func=setupModule

@whimboo or @davehunt please review, thanks.