Update the import of the Task Queue API when it gets out of labs

[Emilien Klein]

When the Task Queue API gets out of labs, the import which is currently
    from google.appengine.api.labs.taskqueue import Task

will need to be changed to
    from google.appengine.api.taskqueue import Task

More details on
http://code.google.com/intl/fr/appengine/docs/python/taskqueue/
and
http://code.google.com/intl/fr/appengine/docs/python/taskqueue/overview.html#Status_of_the_Task_Queue_API