Added

• Support for websockets.
• Support for returning (status, data, headers) from handlers.
• handle_parse_error to App class.

Changed

• ResponseRendererMiddleware now looks up renderers directly off of
  the app object. This means you no longer have to pass them to the
  middleware upon instantiation. This is a breaking change.

  To upgrade, change code that looks like this:

  app = App(
      middleware=[ResponseRendererMiddleware([JSONRenderer()])],
  )

  to:

  app = App(
      middleware=[ResponseRendererMiddleware()],
      renderers=[JSONRenderer()],
  )