CFD-148: Move quick post and activity stream to group dashboard

#220 #221 

The quick post and activity stream in the group dashboard:
![selection_003](https://cloud.githubusercontent.com/assets/7369740/5122924/e024a460-70ae-11e4-9079-4a61846cbeaa.png)

The activity stream after submitting tests:
![selection_004](https://cloud.githubusercontent.com/assets/7369740/5122928/e41c816e-70ae-11e4-8c53-bde76be70763.png)