Bug Fix

@fcurella,
small bug fix on command and celery:
1. The management command is not working now, so I have changed it to use default ``--verbosity`` option.
2. The current setting of ``RECOMMENDS_TASK_RUN = False`` will cause ``recommends_precompute()`` not defined.
3. Suggestion: I think it's better to let user to specify celery jobs, for example, the current ``import`` is not working with latest celery.

Thank you very much. :neckbeard: 

Best Regards,
wgx731