6.1.0-alpha1

• Add v2 of chat.twilio.com.
• Add recording_channels parameter to Participant create and update.
• Add recording_status_callback parameter to Participant create and update.
• Add recording_status_callback_method parameter to Participant create and update.
• Add sip_auth_username parameter to Participant create and update.
• Add region parameter to Participant create and update.
• Add conference_recording_status_callback parameter to Participant create and update.
• Add conference_recording_status_callback_method parameter to Participant create and update.
• Add validity_period parameter to Messages.
• Make endpoint an optional parameter when creating notify bindings.
• Add User, Segment, UserBinding, and SegmentMembership resources to Notify.
• Update Usage API categories.
• Add start_time_before/start_time_after to the Video Rooms API.
• Allow deletion of Wireless RatePlans.