Fix compatibility with Tornado 4

http://stackoverflow.com/questions/24851207/tornado-403-get-warning-when-opening-websocket

gluon/contrib/websocket_messaging.py

@@ -145,6 +145,10 @@ class TokenHandler(tornado.web.RequestHandler):
 
 
 class DistributeHandler(tornado.websocket.WebSocketHandler):
+   
+   def check_origin(self, origin):
+      return True
+
     def open(self, params):
         group, token, name = params.split('/') + [None, None]
         self.group = group or 'default'