Adding jump links to ministers page

- Added jumps links
- Update headers inline with other pages, h1 - increase size, h2's - reduce size add underline i.e. how gov works

https://www.pivotaltracker.com/story/show/44874207
h4s and addressing other pull request feedback

https://www.pivotaltracker.com/story/show/44874207
Pull request - https://github.com/alphagov/whitehall/pull/272