Re-added twitter cards
Improve appearance of upload previews on small width layout
Merge branch 'master' of github.com:MediaCrush/MediaCrush
Merge branch 'master' into thumbnails

Conflicts:
	templates/view.html
Declare certain processing steps as "extra"

These don't get factored into the compression calculation, and they
don't represent the same media. This is currently used to make video
thumbnails distinct from the videos themselves.
List 'extra' files in /hash.json