Revamped the Interaction Graph insight, now Interactions insight.

The Interactions insight (previously Interaction Graph insight) now shows avatars of mentions as insight attachment.

![screenshot from 2013-09-09 23 03 32](https://f.cloud.github.com/assets/1882688/1111168/ff0f20f8-19a2-11e3-8933-151ae377928f.png)