Fix prints
Things like https://gitlab.com/vijeth-aradhya/mediagoblin/blob/multiple-qualities-backend/mediagoblin/media_types/video/processing.py#L169 should be replaced with calls to logging.
Also, text in places like https://gitlab.com/vijeth-aradhya/mediagoblin/blob/multiple-qualities-backend/mediagoblin/media_types/video/processing.py#L338 should be changed from numbers to proper description of what is going on.