message: Fix the styling data driven example.
  This particular example demonstrates how to create a new style set
  by importing rules from an existing theme. Unfortunately, instead of
  creating a new style set this example was simply appending rules to the
  imported style set named 'tilezen' defined in berlin_tilezen_base.json
diff: @@ -47,7 +47,7 @@ export namespace DataDrivenThemeExample {
  }
  },
  styles: {
  - tilezen: [
  + population: [
  ["ref", "countryBorderOutline"],
  ["ref", "waterPolygons"],
  {
  @@ -100,7 +100,7 @@ export namespace DataDrivenThemeExample {
  urlParams: {
  access_token: accessToken
  },
  - styleSetName: "tilezen",
  + styleSetName: "population",
  maxZoomLevel: 17,
  copyrightInfo
  });
  