Issue #37 : Allow passing pulsar.MessageId instance to create_reader() (#95)

(cherry picked from commit 2aaacad)

Author: erichare

pulsar/__init__.py

@@ -882,6 +882,11 @@ def my_listener(reader, message):
             Symmetric encryption class implementation, configuring public key encryption messages for the producer
             and private key decryption messages for the consumer
         """
+        
+        # If a pulsar.MessageId object is passed, access the _pulsar.MessageId object
+        if isinstance(start_message_id, MessageId):
+            start_message_id = start_message_id._msg_id
+
         _check_type(str, topic, 'topic')
         _check_type(_pulsar.MessageId, start_message_id, 'start_message_id')
         _check_type(_schema.Schema, schema, 'schema')