Unsubscribe checkbox

Add back the mass email subscribe/unsubscribe checkbox to account management.

Also simplify the wording, since new features go out in a separate mailing list now.
![screen shot 2014-10-01 at 4 22 40 pm](https://cloud.githubusercontent.com/assets/1757035/4482452/c3b6da1e-49a8-11e4-9016-704214fbdd84.png)