function exports(_selection) {
            _selection.each(function (_data) {
                data = cleanData(_data);

                chartWidth = width - margin.left - margin.right;
                chartHeight = height - margin.top - margin.bottom;

                buildScales();
                buildSVG(this);
                drawDayLabels();
                drawHourLabels();
                drawBoxes();
            });
        }
This function creates the graph using the selection as container
@param  {D3Selection} _selection A d3 selection that represents
                                 the container(s) where the chart(s) will be rendered
@param {HeatmapData} _data The data to attach and generate the chart