Make tox use develop instead of sdist

tox 1.6 was released, which means that we can now take advantage of the
feature we added to it - which is using setup.py develop to install the
code into the virtualenv. The logic was taken from run_tests.sh - so the
performance issues around using tox vs. using install_venv should now be
gone.

This patch requires tox >=1.6.

Change-Id: I505fb530e8047f478e98ce2fd6c01776b147d87f
fix(storage.mongodb): Race condition when creating a claim

This patch forces MessageController.claimed to always query the primary in
order to resolve a race condition in ClaimController.create. The latter
method tags a batch of messages with a claim ID, then immediately
calles claimed() to get a list of messages that were actually updated.

MessageController.claimed is also used by ClaimController.update, so that
request will no longer read from secondaries either. This shouldn't put
much more load on the primary, and may even be desired behavior in the case
that a client creates a claim and immediately attempts to update it, in
which case they could get a "not found" if the new claim hasn't propagated
yet to the secondary being queried.

Change-Id: I8b5cfee1cc6f185ebf53e98fad95a5fc30e021da
Partial-Bug: #1218990
feat(storage): configurable default paging size

This change add the following options to the config file:

    [limits:storage]
    default_queue_paging = 10
    default_message_paging = 10

So that the default value of the  "limit" URI param is now configurable.

This patch also removes the "actions" cruft.

Implements: blueprint configurable-default-paging
Change-Id: Id38295f1e607226a4259be7744e6ce2d7b6de12e
fix(transport.wsgi): JSON home doc missing GET and HEAD hints

GET and HEAD support was added for /v1/queues/{queue_name} but
the home document was not updated accordingly. This patch adds
those methods (AKA verbs) to the home document.

Change-Id: I82bbbf1b6d0735dc2d15faee715175fc724b9423
Merge "fix(transport.wsgi): JSON home doc missing GET and HEAD hints"
Merge "fix(storage.mongodb): Race condition when creating a claim"