Bulk Operation

KAFKA-2387 Remove Consumer from rebalance callback arguments

KAFKA-2387 Expose fetch response high watermark in ConsumerRecords

KAFKA-2387 Have KafkaConsumer.committed() return null when there is no committed offset

KAFKA-2387 Expose offset commit metadata in new consumer

KAFKA-2387 Expose heartbeat frequency in new consumer configuration

KAFKA-2387 Blocking call such as position(), partitionsFor(), committed() and listTopics() should have a timeout

KAFKA-2387 OffsetOutOfRangeException should contain the Offset and Partition info.

KAFKA-2387 CommitType seems not necessary in commit().

KAFKA-2387 subscribe(topic)/unsubscribe(topic) should either take a callback to allow user to handle exceptions or it should be synchronous.