- Update to 4.1:
* If a `.Future` contains an exception but that exception is never
examined or re-raised (e.g. by yielding the `.Future`), a stack
trace will be logged when the `.Future` is garbage-collected.
* New class `tornado.gen.WaitIterator` provides a way to iterate
over ``Futures`` in the order they resolve.
* The `tornado.websocket` module now supports compression via the
"permessage-deflate" extension. Override
`.WebSocketHandler.get_compression_options` to enable on the server
side, and use the ``compression_options`` keyword argument to
`.websocket_connect` on the client side.
* When the appropriate packages are installed, it is possible to yield
`asyncio.Future` or Twisted ``Defered`` objects in Tornado coroutines.