Fix WorkerState.is_alive() not accurate when settings.USE_TZ = True and the local timezone is not UTC
Adds Rockallite Wulf to AUTHORS
Add a stderr and stdout to the Celery commands

The management commands are broken with Django 1.7, which complains because the Command has no std[out|err] attribute.
Disable model validation on Django 1.7.  Closes #336
flakes
Merge branch 'master' of github.com:celery/django-celery