message: use simple js to create range
diff: @@ -2,7 +2,12 @@ import { scaleLinear } from 'd3-scale';
  import ColorScheme from './ColorScheme';
  function range(count) {
  - return [...Array(count).keys()];
  + const values = [];
  + for (let i = 0; i < count; i += 1) {
  + values.push(i);
  + }
  +
  + return values;
  }
  export default class SequentialScheme extends ColorScheme {
  