Opentok

- Fixed an issue with the `opentok.create_session` method

- Added support for the [Captions API](https://tokbox.com/developer/guides/live-captions/)

- Fixed an issue with end-to-end encryption not being called correctly when creating a new session

- Added the `maxBitrate` parameter to the `Client.start_broadcast` method
- Added the `hlsStatus` parameter to the `Broadcast object`
- Added the `streams` parameter so specific streams can be chosen to be included in a SIP call when using the `Client.dial` method

- Fixed broken `opentok.Client.add_archive_stream`, `opentok.Client.remove_archive_stream`, `opentok.Client.add_broadcast_stream` and `opentok.Client.remove_broadcast_stream` methods and tests
- Fixed `opentok.Endpoints.get_archive_stream` and `opentok.Endpoints.get_broadcast_stream` methods

- Added auto-archive improvements to the `opentok.Client.create_session` method
to customize automatically created archives:
- `archive_name` parameter
- `archive_resolution` parameter
- Added the option to append to the user-agent, which can be done with
python
opentok.Client.append_to_user_agent('my-appended-string')

- Added the option to specify audio-only or video-only broadcasts with the new booleans `hasAudio` and `hasVideo`
when starting a broadcast or adding new streams to a broadcast.