Use blocked scoped variables

In addition to using const and let, this also upgrades our linter config and removes lint (mostly whitespace).

examples/cartodb.js

@@ -4,7 +4,7 @@ import TileLayer from '../src/ol/layer/Tile.js';
 import CartoDB from '../src/ol/source/CartoDB.js';
 import OSM from '../src/ol/source/OSM.js';
 
-var mapConfig = {
+const mapConfig = {
   'layers': [{
     'type': 'cartodb',
     'options': {
@@ -15,12 +15,12 @@ var mapConfig = {
   }]
 };
 
-var cartoDBSource = new CartoDB({
+const cartoDBSource = new CartoDB({
   account: 'documentation',
   config: mapConfig
 });
 
-var map = new Map({
+const map = new Map({
   layers: [
     new TileLayer({
       source: new OSM()