WIP first pass at VideoInteractives. 

Lots of incomplete here; just throwing a scaffold at the wall.

https://www.pivotaltracker.com/story/show/48924359
Model specs for VideoInteractives pass
Merge branch 'master' into video-interactives
First cut of controllers and views for VideoInteractives

[#48924359] https://www.pivotaltracker.com/story/show/48924359 - there are still a lot of image tags in here which should be video tags, and we're just storing video URLs, not files.
Adding video scripts, hard-coded video tag
Merge branch 'refs/heads/master' into video-interactives
video.js will do its own fullscreen
Use "poster_url" instead of "url" for VideoInteractives
Use the 'show' partial in authoring mode
Add link to create VideoInteractive
Add VideoSource model [#48924359]

This lets a VideoInteractive have several formats to serve, i.e. mp4, ogg versions of the same video.

https://www.pivotaltracker.com/story/show/48924359
Fixing a bad flash message
Integrating VideoSources with VideoInteractives
rm inaccurate comments
Force the VideoInteractive to have a VideoSource

For some reason if we don't start with at least one VideoSource in place (even an empty one) the nested_form_for falls over. [#48924359]

https://www.pivotaltracker.com/story/show/48924359
Improving display of VideoInteractives
Refactoring resizing of interactives in JS

Pulling the code out of common.js into its own file for refactoring and testing.
Empty spec test for sizing JS file
Testing interactive resizing JS in Jasmine
Icons for video.js controls