Final 2.1.x version
Change log:
f5bcaca Fix trailing whitespaces after previous merge
adb2f9a GH-1287: Detect mis-configured deserialization
36fdb2d GH-1283: Unique client.id for each producer
8c22b78 GH-1247: Polishing
309d28e GH-1247: Only wake consumer while polling
a91ffcc Polishing for previous commit
5f57f4b GH-1196: Use close(Duration) instead of close()