Create admin namespace

https://trello.com/c/iqzQ3SyP/16-create-a-namespace-for-admins

![image](https://cloud.githubusercontent.com/assets/8646429/5171012/4ad033e8-73e2-11e4-9678-a9acd5991a51.png)

All of the `find_charity_by_url` methods are security risks, actually, I think.