WIP simple sponsored content
Merge branch 'master' of https://github.com/guardian/frontend into article-sponsorship
Merge branch 'master' into article-sponsorship
Unit test for sponsored content
Merge branch 'master' of https://github.com/guardian/frontend into article-sponsorship

Conflicts:
	common/app/model/content.scala
Add Carphone Warehouse campaign
Tidy up sponsored articles ready for PROD

- Added SASS (based on article-zone).
- Scala checks the 'paid content' message appears when the sponsored tone is present.
- Switch to turn the feature off/on.
Fix HTML indent

/cc @kaelig
Merge pull request #2679 from guardian/article-sponsorship

Article sponsorship