Changed require_once to include_once
Changed require_once to include_once

to not impose using Composer on users, breaking previous installations

vtrmantovani/celery-php,vtrmantovani/celery-php,smuuf/celery-php,smuuf/celery-php,smuuf/celery-php,xbzbing/celery-php,vtrmantovani/celery-php,xbzbing/celery-php,xbzbing/celery-php