Lightboxes ImageInteractives with colorbox

Finishes [#49883371]. This lightbox uses Colorbox: http://www.jacklmoore.com/colorbox/ and http://github.com/jackmoore/colorbox . The CSS had to be tweaked slightly to make the images work in the Rails asset pipeline; otherwise it's a stock setup.

https://www.pivotaltracker.com/story/show/49883371