Add pointerExtend func to avoid webkitMovementX/Y
Add pointerExtend func to avoid webkitMovementX/Y

Resolves #277, #278

Close #279

bios21/interact.js,chinxianjun/interact.js,adamgruber/interact.js,marian-r/interact.js,Endika/interact.js,mcanthony/interact.js,taye/interact.js,mcanthony/interact.js,taye/interact.js,Endika/interact.js,chinxianjun/interact.js,marian-r/interact.js,adamgruber/interact.js,bios21/interact.js,taye/interact.js