Update example to new eventloop API

Author: SimonFrings

README.md

@@ -15,11 +15,17 @@ Once [installed](#install), you can use the following code to decorate a demo
 function and avoid sending unneeded HTTP requests:
 
 ```php
-$browser = new React\Http\Browser($loop);
+<?php
+
+require __DIR__ . '/vendor/autoload.php';
+
+$browser = new React\Http\Browser();
 
 $fetch = function (int $id) use ($browser) {
     return $browser->get('http://httpbingo.org/status/' . $id)->then(function (ResponseInterface $response) {
         return $response->getStatusCode();
+    }, function (Exception $e) {
+        echo 'Error: ' . $e->getMessage() . PHP_EOL;
     });
 }