Added orange noticon background for unmoderated comments

To test this, you can send yourself an unmoderated comment, or mark any of your existing comment notifications as 'Unapproved'.

![screen shot 2014-10-08 at 11 33 34 am](https://cloud.githubusercontent.com/assets/789137/4564705/a944f46a-4f19-11e4-8041-e9429559ebd0.png)

Fixes #1916