Bump docutils to 0.12

0.10 doesn't exist on internal PyPI.
Correct/clarify App Engine .pth instructions; generally improve doc build howto.
transient_error_retry - Retry transient errors when attempting to insert_tasks, and re-raise if the reinsert fails.
First pass of queue inheritance
Example of context queue inheritance
Merge pull request #149 from aaronkavlie-wf/master

Small doc-related improvements
Merge pull request #155 from markshaule-wf/transient_error_retry

transient_error_retry - Retry transient errors when attempting to insert_tasks, and re-raise if the reinsert fails.
Only reinsert tasks which were not enqueued

If a list of more than one Tasks is given, a raised exception does not
guarantee that no tasks were added to the queue (unless transactional is set
to True). To determine which tasks were successfully added when an exception
is raised, check the Task.was_enqueued property.
Add more doc string context for example
Enable configuration of completion queues & delay
Use more standard Env manipulation in testing
Update queue.yaml to remove uneeded queue
Remove commented out code
Remove line in queue.yaml
Rework config to use standard default behavior
Add in completion config related tests
Update test_queues to handle new queue.yaml
Merge pull request #157 from rosshendrickson-wf/inherit

Inherit Queue for completion check
Merge pull request #156 from tylertreat/reinsert_fix

Only reinsert tasks which were not enqueued
Updating to 1.2.0

Incrementing a minor version to 1.2.0