New UI for SMS Gateway List

As specified in the [Reminders Spec](https://docs.google.com/a/dimagi.com/document/d/1eDlIA3cxF1wgJPESSA1KNo8sMmYmW9s9mlLaGLu8N0w/edit#)

![screen shot 2013-10-17 at 5 30 45 pm](https://f.cloud.github.com/assets/716573/1356215/6d86e14a-3773-11e3-89cf-0bbd2967f79c.png)