IA Pages Index - update layout to match the mockup

@russellholt @jagtalon 

This will be the main PR for the new IA Index layout. As for the plan, I've done the basic two-panes layout and I will then go ahead with the right pane, which still misses topics and templates, and with the general functionality (filtering etc).

@jagtalon, please feel free to begin working on the left pane (the IA list) layout by branching off origin/iaindex_new and creating a PR to this branch.

If you have any questions, suggestions and/or critiques please let me know!

Screenshot:
![screen shot 2014-12-04 at 15 00 48](https://cloud.githubusercontent.com/assets/3652195/5377129/a4cdebc6-807e-11e4-9db6-b37b92f15312.png)

an alternative would be for the `#filters` could be `position: absolute` with `bottom: -1em;` or something like that