Release v2.3.0

New archiving features:

• Automatically archived sessions -- See the archiveMode option of the opentok.createSession() method and the \OpenTok\ArchiveMode class.
• Audio-only or video-only archives -- See the hasAudio and hasVideo options of the opentok.startArchive() method.
• Individual archiving -- See the outputMode option of the opentok.startArchive() method and the \OpenTok\OutputMode class. (#52)
• Paused archives -- When no clients are publishing to a session being archived, its status changes to "paused". See \OpenTok\Archive.status.