Simple view of the views over sessions data on the dashboard

Some big stupid numbers we can all coo at during the alpha testing. We'll put this up on the spare iMac.

_Views over sessions_ is the ratio of users arriving with new sessions to the number of page views over the course of 60 seconds. It approximates page views p/visitor. The higher, the better.
 
![desktop-vs-responsive](https://f.cloud.github.com/assets/84996/1487586/c028b108-4736-11e3-8f6c-cb99f5687495.png)

Hopefully @kaelig won't pick too much at the CSS as it's temporary :astonished: