First draft of header & footer guidance
Tightened intro paragraph. Shorter sentences.

Recast opening sentences to be be user-centric.
Add images of header examples
Merge branch 'master' of github.com:alphagov/government-service-design-manual into header-footer-guidance
Merge branch 'header-footer-guidance' of github.com:alphagov/government-service-design-manual into header-footer-guidance
Update images and template guidance
Update guidance with links
Merge pull request #113 from alphagov/header-footer-guidance

Header footer guidance