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API Changes (Backward-Compatible)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
- Adds ``additional_data`` to ``H2Connection.close_connection``, allowing the
user to send additional debug data on the GOAWAY frame.
- Adds ``last_stream_id`` to ``H2Connection.close_connection``, allowing the
user to manually control what the reported last stream ID is.
- Add new method: ``prioritize``.
- Add support for emitting stream priority information when sending headers
frames using three new keyword arguments: ``priority_weight``,
``priority_depends_on``, and ``priority_exclusive``.
- Add support for "related events": events that fire simultaneously on a single
frame.