support thumbnails for video oembeds
Rid of attachmentImageSize ivar
preliminary video playback support in detail view
animate attachment content resize
Better YouTube support
Print descriptions for oembeds
Support rich oembeds

Note: setting default dimensions to 200x200 if attachment size is unknown
Support CSS in rich attachments
only show thumbnails when we actually have them
better control sizing of rich-text attachment views
More oembed layout fixes
Partially working refactor
Layout fixes for rich text content