mozilla/kitsune — pull request #1153 by willkg (2013-02-20 18:21:25+00:00)
Title: Add Firefox 21, default to Firefox 19.

Pretty sure this is right, but I've never done this before and I couldn't find any docs for it.

I'm basing the changes on commits b12b024 and b4c0f5e7 .

r?