Add (setVolume:) (getContentType) (getFileExtension) for FSAudioStream

(setVolume:) need to control sound volume
(getContentType) (getFileExtension) need to get file extension of audio stream, like @"mp3" or @"aac" to record and play recorded file, because, for example:

AVPlayer will not play file like "track", but will play file "track.mp3", but if file extension wrong it will not play again. That's why we need to be able get file extension of current recorded file