fix json code, we dont have async here.

tornado/server.py

@@ -11,12 +11,9 @@ from tornado.options import options
 tornado.options.define('port', default=8888, type=int, help=(
     "Server port"))
 
-
 db = motor.MotorClient("127.0.0.1").open_sync().hello_world
 
 class JsonSerializeTestHandler(tornado.web.RequestHandler):
-    @tornado.web.asynchronous
-    @gen.coroutine
     def get(self):
         obj = dict(message="Hello, World!")
         self.write(obj)