Private group

Do not show other member in private group. 
Only admin and group owner should have the members displayed.

To test:
 * Log in as user-1 
![user-1](https://f.cloud.github.com/assets/1022396/1521435/fdc9152e-4b92-11e3-8283-7aad8dc5a268.png)
 * log in as user-2
![user-2](https://f.cloud.github.com/assets/1022396/1521437/05ce8c22-4b93-11e3-9d3f-971cf1100acc.png)
 * log in as user-6
![user-6](https://f.cloud.github.com/assets/1022396/1521443/0f26dc84-4b93-11e3-9b27-fb6c10a04020.png)