Switch to using govuk_admin_template

* Upgrade from Bootstrap 2 to Bootstrap 3
* Minor feature changes agreed with Lisa:
  * Remove the beta flag
  * Move bookmarked needs and browser tools to main navigation
  * Remove the feedback email from the bottom, which wasn't being used
* Delete styles now available within the gem
* Upgrade formtastic and formtastic bootstrap
* Update Bootstrap html for alerts, buttons, icons, breadcrumbs, forms, grids
* Functionality should be exactly the same

![screen shot 2014-05-28 at 16 51 19](https://cloud.githubusercontent.com/assets/319055/3106880/f6d4785c-e67f-11e3-94e9-7207012d87ff.png)