Add parent id and request id to Async

Add a parent id and request id to the Async object. The parent id will be passed
down to "children" asyncs. This will allow us to track the chain/graph of asyncs
without developer intervention.
Switch _function_path to just return function_path

Better handling of deprecated function to ensure backwards compatibility.
Fix stupid property bug

function_path is a property not a method so don't parens is :)
Merge pull request #147 from beaulyddon-wf/add_parent_id_to_asyncs

Add parent id and request id to Async
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