Resolve Deprecation/Warning Messages That Occur During Testing

[dixonwhitmire]

The attached file contains the warnings emitted during lib-kafka's test case execution (running with pytest)

Generally, the warnings fall into three categories:

• using a deprecated logging method, logger.warn
• the asynctest's library uses the soon to be deprecated @coroutine decorator rather than the async and await keywords.
• some of the producer/consumer tests expect to run against an active Kafka instance.

warnings.log