Move to responsive site

This PR updates the Engine to work within the fronted repository. As rough summary of changes:

* Update to ruby 2.1.2
* Update to Rails 4.1
* Change Google Analytics Conversion tracking to Google Tag Manager (see similar [car cost tool commit](https://github.com/moneyadviceservice/car_cost_tool/commit/c85052672cceb89839002d001641ccab350140b3) for details)
* Remove CSS Namespace
* Adds appropriate category_id for each tool within the engine
* Add in page titles / description meta tags already in use on the existing live tools