Fast bitrate switch

Example showing how to aggressively replace existing segments in the buffer when switching up in quality. When fastswitch is enabled and an up-switch in quality is performed, the next fragment is not appended at the end of the current buffer range but closer to the current time.

Note, When ABR down-switch is detected, we appended the lower quality at the end of the buffer range to preserve the higher quality media for as long as possible.