[DISCUSS] KIP-381 Connect: Tell about records that had their offsets flushed in callback

[Per Steffensen]

Please help make the proposed changes in KIP-381 become reality. Please 
comment.

KIP: 
https://cwiki.apache.org/confluence/display/KAFKA/KIP-381%3A+Connect%3A+Tell+about+records+that+had+their+offsets+flushed+in+callback

JIRA: https://issues.apache.org/jira/browse/KAFKA-5716

PR: https://github.com/apache/kafka/pull/3872

Thanks!