Fix email input in settings (bug 1094723)

Before

![account_settings___firefox_marketplace 2](https://cloud.githubusercontent.com/assets/1514/4937320/5a209a96-65c2-11e4-9205-bb3f791093c9.png)
![account_settings___firefox_marketplace 4](https://cloud.githubusercontent.com/assets/1514/4937321/5c2a366c-65c2-11e4-9f54-c37e57c7cc88.png)

After

![account_settings___firefox_marketplace 3](https://cloud.githubusercontent.com/assets/1514/4937326/5fc98336-65c2-11e4-8d9e-04185020af46.png)
![account_settings___firefox_marketplace](https://cloud.githubusercontent.com/assets/1514/4937328/634ce7c8-65c2-11e4-8907-9d49272a1d29.png)