Scope styles to govuk class

- Prevent global govuk-helper styles affecting header or footer
- Import govuk-helper as a single file with multiple includes for all
base stylesheets
- Ensure two space indent is used
- Add class for full width main content
Merge branch 'gh-pages' of github.com:alphagov/design-patterns into gh-pages

Conflicts:
	assets/stylesheets/base-ie6.css
	assets/stylesheets/base-ie7.css
	assets/stylesheets/base-ie8.css
	assets/stylesheets/base.css
	assets/stylesheets/example-form/example-form.css