Edit listings

https://trello.com/c/Rlfr8eTn/41-edit-listings

![image](https://cloud.githubusercontent.com/assets/8669803/5094558/e4485d6e-6f2f-11e4-9e0c-449068d9c077.png)

![image](https://cloud.githubusercontent.com/assets/8669803/5094559/ee9b5ef6-6f2f-11e4-91c7-712ff83740d2.png)

![image](https://cloud.githubusercontent.com/assets/8669803/5094563/f413118a-6f2f-11e4-8bfa-fd6ad6496811.png)
I do not; if a part of the update would fail, it just reverts that line to pre-edit