code: function buildScales() {
              colorScale = d3Scale.scaleLinear()
                  .range([colorSchema[0], colorSchema[colorSchema.length - 1]])
                  .domain(d3Array.extent(data, getValue))
                  .interpolate(d3Interpolate.interpolateHcl);
          }
docs: Creates the scales for the heatmap chart
  @return void