queue: Make queue implementation swappable

This commit makes it possible to swap out the queue implementation for
anything satisfying h.queue.interfaces.IQueueHelper, i.e. providing a
"get_reader" and "get_writer" methods.
queue: Add a thread-local queue implementation

This adds an implementation of a queue interface that mirrors the NSQ
reader/writer paradigm but uses thread-local gevent queues to pass
messages around.

Changes development.ini to default to this local queue implementation.