Update the changelog

Author: dasch

CHANGELOG.md

@@ -9,6 +9,7 @@ Changes and additions to the library will be listed here.
 - Drops support for Kafka 0.9 in favor of Kafka 0.10 (#381)!
 - Handle cases where there are no partitions to fetch from by sleeping a bit (#439).
 - Handle problems with the broker cache (#440).
+- Shut down more quickly (#438).
 
 ## v0.4.3