KAFKA-6690 Priorities for Source Topics

[Nick]

Hi all,

I picked up KAFKA-6690 Priorities for Source Topics.
  https://issues.apache.org/jira/browse/KAFKA-6690

In the ticket I made some notes about extending the API to incorporate 
topic priorities.

For implementation, I was thinking of filtering out lower priority 
topics in method Fetcher.fetchablePartitions.

Thanks for any input.

Regards,
--
    Nick