Added changelog entry for 0.3.0
CHANGES
--------
+0.3.0 (XXXX-XX-XX)
+^^^^^^^^^^^^^^^^^^
+
+* Changed ConsumerRebalanceListener to support either function or coroutine
+ for `on_partitions_assigned` and `on_partitions_revoked` callbacks (PR #190
+ by @ask)
+*
+
0.2.3 (2017-07-23)
^^^^^^^^^^^^^^^^^^
