Upgrade Rails to 4.0.9

Latest security patches, and staying up to date.
Update rails-sass to 4.0.2

This required dropping a completely missing file and surrounding
selectors from the SCSS.
Merge pull request #45 from alphagov/rails-409

Upgrade Rails to 4.0.9
Merge commit 'a2766879b05eb1e7f9f34a896853ffd6d43776fb' into HEAD