Implements infinite scrolling

- Implements infinite scrolling by binding to the scroll method
- Changes pagination from a clickable div to a nice looking spinner when loading messages
- Adds silence_mentions to make sure mentions are not fired when loading old messages
- When pulling old messages we do not navigate to oldest message anymore
- Fixes #186
- Fixes #180
Updated some gems that were updated to work with Rails 3.2.13
Fixes to deal with empty channels
Merge pull request #238 from gabceb/180

Implements infinite scrolling