Need a global shutoff setting.

[JnBrymn]

For the purposes of testing and debugging it would be useful to have a global shutoff value that would cause all @background decorated tasks to run synchronously. Celery has this with it's task-always-eager setting.

I'm probably being naive, but an easy fix would be, on this line stick

if os.environ('TASK_ALWAYS_EAGER') == 'TRUE':
    return self.task_function()

[philippeowagner]

This is a good idea.

Maybe the env variable name should be defined in the settings.py.

Another option is a file. If present, ...

[schmave]

Seems like this is a duplicate of #176