code: function RotateBy (opts) {
      RotateBy.superclass.constructor.call(this, opts)
  
      this.angle = opts.angle
  }
docs: @class
  Rotates a cocos.Node object to a certain angle by modifying its rotation
  attribute. The direction will be decided by the shortest angle.
  
  @memberOf cocos.actions
  @extends cocos.actions.RotateTo
  
  @opt {Float} duration Number of seconds to run action for
  @opt {Float} angle Angle in degrees to rotate by