Marking videos as viewed

[hdweiss]

Thanks for the plugin, it works really well. There seems to be one issue with marking of videos as viewed though. After watching a single video in a section, all videos in the section are marked as viewed. Additionally the view state isn't displayed as a little checkmark next to the video in the plugin.

Have only tried it with the "model thinking" course. (https://class.coursera.org/modelthinking-009)

[cancan101]

PRs are welcome :-)
I probably won't have time to address this any time soon.