function Helpers(barCtx) {
      _classCallCheck(this, Helpers);
      this.w = barCtx.w;
      this.barCtx = barCtx;
    }
handleBarDataLabels is used to calculate the positions for the data-labels
It also sets the element's data attr for bars and calls drawCalculatedBarDataLabels()
After calculating, it also calls the function to draw data labels
@memberof Bar
@param {object} {barProps} most of the bar properties used throughout the bar
drawing function
@return {object} dataLabels node-element which you can append later