code: function exports(_selection) {
              _selection.each(function(_data) {
                  chartWidth = width - margin.left - margin.right;
                  chartHeight = height - margin.top - margin.bottom;
                  data = cleanData(_data);
  
                  if (hasTitle()) {
                      chartWidth -= legendSpacing;
                  }
  
                  buildScales();
                  buildSVG(this);
                  buildAxis();
                  drawBullet();
                  drawTitles();
                  drawAxis();
  
              });
          }
docs: 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 {BulletChartData} _data   The data to attach and generate the chart