fall back to generic content rating body (bug 932074)

Depends on https://github.com/mozilla/zamboni/pull/1308

Mocked at https://github.com/mozilla/flue/pull/6

Screenshot of falling back to generic region (I mocked the region to be 'lol'):

![screen shot 2013-10-28 at 6 13 03 pm](https://f.cloud.github.com/assets/674727/1425359/7a3db144-4037-11e3-9fea-06ae09239950.png)