Reset animation in shiny

[calebasaraba]

Thank you so much for this amazing package -- I saw your talk at the NYR conference and it inspired me to use rthreejs!

On a similar vein to #52 (clearing a shiny graph), once an animated scatterplot is rendered in shiny, a second rendering call will reset the canvas but the animation will resume at whatever scene the prior animation had gotten up to instead of resetting from the beginning.

[bwlewis]

Shoot! Yes, good catch.