Add a single view of all recent deployments

This adds a new view to the release app, to show a list of the twenty-five most recent deployments. This is something that we already collect the data on, but don't surface easily without having to scan the entire application version table. Deployments to staging and production are highlighted in the list.

![recent-releases](https://f.cloud.github.com/assets/71922/2247727/5ccf3118-9d71-11e3-8733-c0cbd7a12c40.png)