Incompatable with Django < 1.2

[esatterwhite]

The current implementation is incompatible with Django 1.0 & 1.1.x
namely because the 'available_attrs' method did not exist in the decorators module of django's utils. This makes it impossible to import the task decorator from ztask.

[esatterwhite]

Additionally, it looks as if you are not even calling the available_attrs method from anywhere in the code... that would be an easy fix