Update default topojsonURL to point to new maps

Author: camdecoster

src/plot_api/plot_config.js

@@ -369,7 +369,8 @@ var configAttributes = {
     topojsonURL: {
         valType: 'string',
         noBlank: true,
-        dflt: 'https://cdn.plot.ly/',
+        // TODO: Switch the default back to 'https://cdn.plot.ly/' once we remove the legacy maps
+        dflt: 'https://cdn.plot.ly/un/',
         description: [
             'Set the URL to topojson used in geo charts.',
             'By default, the topojson files are fetched from cdn.plot.ly.',