Allows json in cfg file

like so:

[CELERY]
# Celery app configuration goes here
# cf http://docs.celeryproject.org/en/latest/configuration.html for details
CELERY_ALWAYS_EAGER = False
CELERY_CREATE_MISSING_QUEUES = True
CELERY_DEFAULT_QUEUE = 'default'
CELERY_QUEUES = {
        "default": {
            "exchange": "default",
            "exchange_type": "topic",
            "binding_key": "tasks.#"
        },
        "precache": {
            "exchange": "precache",
            "exchange_type": "topic",
            "binding_key": "tasks.precache.#"
        },
        "ingest": {
            "exchange": "ingest",
            "exchange_type": "topic",
            "binding_key": "tasks.ingest.#"
        }
    }