python: fix echoserver working on Python 2.7.2

see also msgpack-rpc/msgpack-rpc#45

Traceback (most recent call last):
  File "echoserver.py", line 51, in <module>
    print "Serving on localhost:%d\n" % (port,)
TypeError: %d format: a number is required, not tuple

Author: TAKANO Mitsuhiro

example/echoserver.py

@@ -48,4 +48,4 @@ def serve(daemon=False):
 
 if __name__ == '__main__':
     port = serve(False)
-    print "Serving on localhost:%d\n" % (port,)
+    print "Serving on localhost:%d\n" % port[1]