Fix behaviour for anonymous givers/receivers

fixes gratipay/gratipay.com#2648

Thought I'd quickly send this before renaming changes start to flow in.

The styling does look a bit awkward though... 

![gratipayanon](https://cloud.githubusercontent.com/assets/3893573/4090685/0e48e43e-2f80-11e4-8215-db666819cc49.png)