Fix consent options to bottom of screen

This keeps the consent options always visible on the consent doc. Hopefully this will make it more apparent to users that they need to do something.

Issue #50

![screen shot 2014-11-21 at 5 21 05 pm](https://cloud.githubusercontent.com/assets/4962198/5152268/b79450d6-71a3-11e4-9273-e50f75b2b032.png)

![screen shot 2014-11-21 at 5 21 08 pm](https://cloud.githubusercontent.com/assets/4962198/5152269/bbe8f952-71a3-11e4-8cb2-e6f412f4cc9d.png)
![screen shot 2014-11-21 at 5 24 57 pm](https://cloud.githubusercontent.com/assets/4962198/5152270/beef286a-71a3-11e4-9e29-d58ae1852804.png)