ctor(duration, xStrength, yStrength, originalPosition) {
    cc.ActionInterval.prototype.ctor.call(this);
    this.initWithDuration(duration, xStrength, yStrength, originalPosition);
  }
Animates a cc.node as if it was shaking randomly.
@function
@param {Number} duration
@param {Number} xStrength - how far out in the x direction object will travel in BOTH directions
@param {Number} yStrength
@param {Vec2} originalPosition
@return {FigureEight}