v1.6.0

v1.6.0 is a feature release with the following features, fixes and enhancements:

• Bundles librdkafka v1.6.0 which adds support for Incremental rebalancing,
  Sticky producer partitioning, Transactional producer scalabilty improvements,
  and much much more. See link to release notes below.
• Rename asyncio.py example to avoid circular import (#945)
• The Linux wheels are now built with manylinux2010 (rather than manylinux1)
  since OpenSSL v1.1.1 no longer builds on CentOS 5. Older Linux distros may
  thus no longer be supported, such as CentOS 5.
• The in-wheel OpenSSL version has been updated to 1.1.1i.
• Added Message.latency() to retrieve the per-message produce latency.
• Added trove classifiers.
• Consumer destructor will no longer trigger consumer_close(),
  consumer.close() must now be explicitly called if the application
  wants to leave the consumer group properly and commit final offsets.
• Fix PY_SSIZE_T_CLEAN warning
• Move confluent_kafka/ to src/ to avoid pytest/tox picking up the local dir
• Added producer.purge() to purge messages in-queue/flight (@peteryin21, #548)
• Added AdminClient.list_groups() API (@messense, #948)
• Rename asyncio.py example to avoid circular import (#945)

confluent-kafka-python is based on librdkafka v1.6.0, see the librdkafka release notes
for a complete list of changes, enhancements, fixes and upgrade considerations.