Persist student progress in video.

Student logins to edx, plays video, selects position, closes
browser, opens video, position is restored.

BLD-385
Addressing David's comments.
Debug.
Removed ipdb.
Bug fix.

Changed from the already used position to saved_video_position.
Update video_module.py

Fixing pep8 errors.
Update video.py

Fixing pep8 errors.
Update video.py

Fixing pep8 errors.
Update video.py

Fixing pep8 errors.