Improve status messages on confirmation

This pull request updates the confirm template, making the response clearer, particularly when it comes to confirmation errors.

|state|screenshot|
|-------|--------------|
|success|![screen shot 2015-01-01 at 9 07 41 pm](https://cloud.githubusercontent.com/assets/860934/5591982/1895d42e-91fa-11e4-87c0-331ff3597ef0.png)|
|failure|![screen shot 2015-01-01 at 9 07 56 pm](https://cloud.githubusercontent.com/assets/860934/5591983/1e85df64-91fa-11e4-9a4e-8c4339296eef.png)|

Note: this is for the `/confirm` route, *not* email templates.