Show retries in specific queue

I often want to see just retries in the specific queue. This patch adds support for "retries/in/#{queue}" endpoint which will filter the failures. Clicking the name of the queue in the Retries view will show only the filtered failures.

![retries-in-queue](https://f.cloud.github.com/assets/19076/1172342/531f7b5c-211e-11e3-9422-4a55edd9a803.gif)

I have only included English localization, since I don't speak any other languages that sidekiq supports.