adding sign up and video cta to /features

Adding a sign up CTA as well as a link to the forthcoming videos page (/how-to) to bottom of features

![image](https://cloud.githubusercontent.com/assets/1246990/3271584/e9616492-f30d-11e3-90e6-52252aeaee06.png)

Better to break this up a bit for better legibility, eg:

<p>
   Copy
   <a href="">Link</a>
</p>