Add "latest changes" styling.

https://www.pivotaltracker.com/story/show/79185352

Target: https://s3.amazonaws.com/prod.tracker2/resource/38181260/latest%20view%20minus%20feed.png?AWSAccessKeyId=AKIAIKWOAN6H4H3QMJ6Q&Expires=1415353588&Signature=H0%2F8nlc7sleY6x3eWgUK7b3Zad0%3D

Actual:
![screenshot 2014-11-07 09 29 37](https://cloud.githubusercontent.com/assets/109225/4952573/3fe57a66-6676-11e4-83a3-c8e76df90825.png)

(ignore the missing beta image)