Consumer.consume() auto-commits even when disabled by 'enable.auto.commit'

[Qgel]

consume() currently always auto-commits, regardless of the setting for 'enable.auto.commit'. I believe this is an upstream issue in confluent-kafka, see confluentinc/confluent-kafka-python#1299

It might be nice to adjust the example in the readme in the meantime to use poll() instead (which works as expected), or add a comment to it that the functionality is currently broken.

I'll be happy to make a PR for an updated example if that's desired. Might save someone else some time trying to track down this issue.