(WIP) Video Captions

This from the hackathon.

Progress
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- [x] Good look
- [x] Adapts to the both the video and the screen size
- [x] Allows user to view both transcript and closed captions
- [x] User can re-position the closed captions (vertically)
- [ ] Saves the user preference on cookies
- [ ] Unclean code
- [ ] Need UX review of transcript toggle
- [ ] Totally removed the side-bar, we should both
- [ ] Not configurable by django-settings (to let dev ops configure if they want to keep the the CC button pointing to transcripts)
- [ ] Still an xmodule
- [ ] Repositioning closed captions while video is playing is not smooth
- [ ] Use "dragabilly" library instead of jQuery UI, for moving the closed captions (if we keep the feature)
- [ ] In code todo's?

Screenshots
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**Captions Only**
![image](https://cloud.githubusercontent.com/assets/645156/5489569/2b19a21a-86d3-11e4-9bd5-2b2a304a6932.png)

**Captions and Transcripts**
![image](https://cloud.githubusercontent.com/assets/645156/5489575/39604e78-86d3-11e4-8908-deff55827a6b.png)

**None**
![image](https://cloud.githubusercontent.com/assets/645156/5489581/3fba1cae-86d3-11e4-9755-36e3481972f4.png)

Too-long don't read stuff on the wiki
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https://openedx.atlassian.net/wiki/display/A11Y/Media