Add feedback link

To improve the product for users, we need feedback.
This adds a feedback link in place of the updated date and moves
the updated date to sit with the departmental meta data.
Updating tests

Tests updated to reflect changes to mark up after adding feedback link.
As the last updated date is now moved into the description list metadata
we no longer need to test for presence of a colon as its added automatically
via CSS. Thanks for your help with this @tommyp
Merge pull request #107 from alphagov/add-feedback-link

Add feedback link