Bluesky-kafka

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* added timeout parameter to ``utils.get_cluster_metadata()`` and ``utils.list_topics()``
* put release history in reverse chronological order

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* added ``continue_polling`` parameter to ``BlueskyConsumer.start()``
* added ``utils.py``
* added ``BlueskyKafkaException``
* split tests into multiple files
* create and clean up topics for each test
* simplified produce/consume tests to run in one process
* configured live logging in ``pytest.ini``
* switched from Travis CI to GitHub Workflow for continuous integration

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* added ``BlueskyConsumer``
* added ``MongoConsumer``
* added supervisor configuration file for ``mongo_normalized_consumer.py``
* rewrote ``RemoteDispatcher`` to use ``BlueskyConsumer``
* changed default serialization method to ``MessagePack``