Change Request: frameCount

[tonytoms]

Hi.
Thanks a lot for the awesome lib.
I was using it in my react app with the SpriteAnimator component.
I finding a naming convention bit weird. The 'framecount' is actually not the total frames that will be played from the 'startFrame'. It's actually the ending frame.
That is ,
startFrame=2 ,framecount=5 => will make the lib play frames 2,3 and 4.
It's a bit confusing.
So, it's a humble suggestion to rename framecount to endframe.