Tidy up the email alert subscription page

https://www.pivotaltracker.com/story/show/81950824

Working with @futurefabric, this branch includes some tidying up of the email subscription page, and adds breadcrumbs.

Before:
![before](https://cloud.githubusercontent.com/assets/71922/5127255/08f08e6a-70cb-11e4-966a-cbff39e38266.png)

After:
![after](https://cloud.githubusercontent.com/assets/71922/5127257/0d7b9dda-70cb-11e4-9ab5-e493bcc10047.png)

Is this only wanted on desktop or mobile as well?