Cleanup change email form when there's a pending change

* Add missing Bootstrap 3 classes
* Move cancel and resend buttons beneath form field
* Visually separate the change email form and the resend email form
* Improve re-sent email copy

Before:
![screen shot 2014-10-13 at 11 23 18](https://cloud.githubusercontent.com/assets/319055/4612117/41140acc-52c3-11e4-9db7-b702236a6500.png)

After:
![screen shot 2014-10-13 at 11 23 45](https://cloud.githubusercontent.com/assets/319055/4612120/45240d4c-52c3-11e4-9ea0-2970991d8961.png)