Rename EIM index

When using the index to construct a fake manual the title was incorrectly
being set as EIM Main Contents.
Adding placeholder JSON for EIM updates
Refactor Manual fetching to before_filter
Adding route and controller action for #updates
Rendering updates view

Adding a link to the updates from the header and an updates view. The
ChangeNotesPresenter takes the updates JSON and organises it by Year,
then by Day, then by Document.
Merge pull request #54 from alphagov/change-notes-for-front-end-users

Change notes for front end users