Whitespace cleanup
Making block-N classes be full-width on mobile

Part of https://www.pivotaltracker.com/story/show/67299528
Increase of padding-bottom on page Headings

Part of https://www.pivotaltracker.com/story/show/67299528
Increase of padding-bottom on block containers

Part of https://www.pivotaltracker.com/story/show/67299528
Merge pull request #94 from alphagov/redesign-tidy-up

Redesign tidy up

https://www.pivotaltracker.com/story/show/67299528