Support EXT-X-CUE-OUT:Elapsed/Duration format

[bbayles]

This PR updates the EXT-X-CUE-OUT parsing function to support a format that I encountered in the wild.

Instead of the "SCTE-35 enhanced" style, which is already supported:

#EXT-X-CUE-OUT-CONT:ElapsedTime=$ELAPSEDTIME,Duration=$DURATION,SCTE35=$SCTE35

This has:

#EXT-X-CUE-OUT-CONT:$ELAPSEDTIME/$DURATION

[bbayles]

This is Elemental style, for what it's worth.

[mauricioabreu]

@bbayles sorry for the long delay. I'll do the best I can so it does happen again.

Good job!