Saved work in progress
Changed the purpose and the relationships of media, media_display and media_type
type in media display should not be null
Fixed doc for MediaType
Added tests to reach the displays from the media
Added many_to_many between media and media_display using media_type as bridge
Added tests for $product->media_by_type('image')
Instead of returning a list, return a resultset
Added display_uris to Media
Added display_uri to Media
Fixed the variant tests
Added documentation
Merge pull request #59 from melmothx/topic/media-display

Overhaul media result classes.