Users can add and remove friends

![image](https://cloud.githubusercontent.com/assets/8655639/5363403/e9588358-7fa9-11e4-8f2e-8bde118df52b.png)

What happens if the `friend_request` isn't saved? Since there's no `else`, I'd just do `redirect_to friend` without the `if`, since the `if` doesn't gain you anything in this case.