Consumers

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- Fix documentation.

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- Change consumer to be any callable type.
- Add consumer arg and kwarg specification.
- Change consumer process naming.

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- Remove ``Pool.start()`` in favor of starting the pool upon Pool
instantiation.
- Rename ``Pool.stop()`` to ``Pool.join()``
- Add ``Pool.close()`` to drain the queue and shutdown consumer processes in
the background.
- Add ``Pool.terminate()`` to kill the consumer processes.
- Refactor a few things.

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- Essentially an API rewrite on what consumers are and how they consume.

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- Added queue results.
- Removed mechanism for queues to manage related queues.

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- Fixed consumers being created in the master process before being forked into
separate processes.