Twilio

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- Add several missing `<Gather>` attributes.
- `partial_result_callback`
- `partial_result_callback_method`
- `language`
- `hints`
- `barge_in`
- `acknowledge_sound_url`
- `input`
- Remove client-side max page size validation.
- Support `announce_url` and `announce_url_method` on Conference Participants.
- TwiML docstring corrections.

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- Remove support for Python 2.6.
- Add `locality` field to `AvailablePhoneNumbers`.
- Add `origin` field to `IncomingPhoneNumbers`.
- Add `in_locality` parameter to `AvailablePhoneNumbers`.
- Add `origin` parameter to `IncomingPhoneNumbers`.
- Add new sync categories to `UsageRecords`.
- Support unicode in `validation_client`.
- Add `muted` parameter to `<Conference>` Twiml.

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- Rename RoomList to RoomRecordingsList.

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- Add video domain.
- Update usage record categories.
- Add `get_page` method for reentrant paging.

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- Allow *kwargs in TwiML Gather

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- Add Task verb to VoiceResponse
- Add Echo verb to VoiceResponse
- Add Sim verb to VoiceResponse