fixed lint

playground/e2e/app.test.js

 });
 
 describe('reload app', () => {
-  before(function (done) {
+  before((done) => {
     simulator.reloadReactNativeApp(done);
   });
+
   it('shows welcome screen', () => {
     expect(elementByLabel('React Native Navigation!')).toBeVisible();
   });

playground/src/containers/SimpleScreen.js

   onClickPop() {
     Navigation.on(this.props.id).pop();
   }
-  
+
   onClickPush() {
     Navigation.on(this.props.id).push({
       name: 'navigation.playground.SimpleScreen',
       passProps: {
-        stackPosition: this.props.stackPosition + 1,
+        stackPosition: this.props.stackPosition + 1
       }
     });
   }