Have consistent string formating

Use the %d operator in both consumer and producer for the offset.

Author: hrchu

examples/producer.py

@@ -45,7 +45,7 @@ def delivery_callback(err, msg):
         if err:
             sys.stderr.write('%% Message failed delivery: %s\n' % err)
         else:
-            sys.stderr.write('%% Message delivered to %s [%d] @ %o\n' %
+            sys.stderr.write('%% Message delivered to %s [%d] @ %d\n' %
                              (msg.topic(), msg.partition(), msg.offset()))
 
     # Read lines from stdin, produce each line to Kafka