Update design for generalisation

This PR implements the design changes to bring the hmrc-manual and the manual designs closer together.

The design:
![screen shot 2014-05-21 at 17 13 22](https://cloud.githubusercontent.com/assets/68009/3043135/0c73abb0-e103-11e3-9069-807db8961892.png)

The before:
![screen shot 2014-05-21 at 17 13 18](https://cloud.githubusercontent.com/assets/68009/3043140/1894de78-e103-11e3-9f15-47cd0e8ca9fb.png)

The after:
![screen shot 2014-05-21 at 17 13 01](https://cloud.githubusercontent.com/assets/68009/3043143/1f689636-e103-11e3-8dcf-df530c70ea89.png)