clean up buttons in footer of Account Settings page

# mobile width
![settings-mobile](https://cloud.githubusercontent.com/assets/203725/5040402/0baa8074-6b63-11e4-8189-89d1eb00b8e5.png)

# desktop width
![settings-desktop](https://cloud.githubusercontent.com/assets/203725/5040403/0baa8952-6b63-11e4-9de1-f6729a3e3bc9.png)

setting the background on the parent element (`footer`) instead of on every single child (`p.extras`).