In article video poster image

Poster image is now woven into the video. This is at the mercy of whatever picture comes out of the API as the 'still image' field. We might want to have a chat with the people who upload them.

If the video is the first thing inside the body (i.e. the very first HTML element inside the body) then the main picture will be hidden.
Merge branch 'master' of github.com:guardian/frontend into in-article-video
Merge branch 'master' of github.com:guardian/frontend into in-article-video

Conflicts:
	data/database/0ca267a5a9906e7988de0c7a413ad4bd3c48a4ed
Merge branch 'master' of github.com:guardian/frontend into in-article-video

Conflicts:
	data/database/b3aa5b3f03ee1a6abbb0e49a22ffeb68ae6ce7b9
Merge branch 'master' of github.com:guardian/frontend into in-article-video

Conflicts:
	data/database/b3aa5b3f03ee1a6abbb0e49a22ffeb68ae6ce7b9
Merge branch 'master' of github.com:guardian/frontend into in-article-video
Switch back to previous version of grunt-contrib-sass
Merge pull request #603 from guardian/in-article-video

In article video