Log Message:
Update to 4.0.2:

Bug fixes
~~~~~~~~~

* Fixed a bug that could sometimes cause a timeout to fire after being
  cancelled.
* `.AsyncTestCase` once again passes along arguments to test methods,
  making it compatible with extensions such as Nose's test generators.
* `.StaticFileHandler` can again compress its responses when gzip is enabled.
* ``simple_httpclient`` passes its ``max_buffer_size`` argument to the
  underlying stream.
* Fixed a reference cycle that can lead to increased memory consumption.
* `.add_accept_handler` will now limit the number of times it will call
  `~socket.socket.accept` per `.IOLoop` iteration, addressing a potential
  starvation issue.
* Improved error handling in `.IOStream.connect` (primarily for FreeBSD
  systems)