Use blocked scoped variables

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

test/spec/ol/events/event.test.js

@@ -4,30 +4,30 @@ describe('ol.events.Event', function() {
 
   describe('constructor', function() {
     it('takes a type as argument', function() {
-      var event = new Event('foo');
+      const event = new Event('foo');
       expect(event.type).to.be('foo');
     });
     it('does not set the propagationStopped flag', function() {
-      var event = new Event('foo');
+      const event = new Event('foo');
       expect(event.propagationStopped).to.be(undefined);
     });
   });
 
   describe('#preventDefault', function() {
     it('sets the propagationStopped flag', function() {
-      var event = new Event('foo');
+      const event = new Event('foo');
       event.preventDefault();
       expect(event.propagationStopped).to.be(true);
     });
     it('is the same as #stopPropagation', function() {
-      var event = new Event('foo');
+      const event = new Event('foo');
       expect(event.stopPropagation).to.equal(event.preventDefault);
     });
   });
 
   describe('ol.events.Event.preventDefault', function() {
     it('calls preventDefault on the event object', function() {
-      var event = {
+      const event = {
         preventDefault: sinon.spy()
       };
       Event.preventDefault(event);
@@ -37,7 +37,7 @@ describe('ol.events.Event', function() {
 
   describe('ol.events.Event.stopPropagation', function() {
     it('calls preventDefault on the event object', function() {
-      var event = {
+      const event = {
         stopPropagation: sinon.spy()
       };
       Event.stopPropagation(event);