v2.2.0

CHANGES:

• Previously if the client closed the connection while cohttp was
  handling a request, the server would crash (by default, unless the
  user overrode that using on_exn or changing Lwt's async exception
  handler). Now, cohttp will just log this at info level and
  continue. Exceptions produced by user code are logged as errors,
  while other exceptions generated by cohttp call back to the conduit
  exception handler, as before. (#669 @talex5)