fix for 5.4

Author: pulkitjalan

README.md

@@ -136,4 +136,8 @@ $requester->addLogger($log);
 
 // request and response logged to file
 $requester->url('example.com')->get();
+
+// Use the second param to update the format
+$requester = new Requester(new GuzzleClient());
+$requester->addLogger($log, 'DEBUG');
 ```

src/Requester.php

@@ -3,7 +3,6 @@
 namespace PulkitJalan\Requester;
 
 use GuzzleHttp\Client as GuzzleClient;
-use GuzzleHttp\Subscriber\Log\Formatter;
 use GuzzleHttp\Subscriber\Log\LogSubscriber;
 use GuzzleHttp\Subscriber\Retry\RetrySubscriber;
 use PulkitJalan\Requester\Exceptions\InvalidUrlException;
@@ -114,8 +113,8 @@ public function getGuzzleClient()
      */
     public function addLogger($logger, $format = 'CLF')
     {
-        if (defined(Formatter::class.'::'.$format)) {
-            $format = constant(Formatter::class.'::'.$format);
+        if (defined('GuzzleHttp\Subscriber\Log\Formatter::'.$format)) {
+            $format = constant('GuzzleHttp\Subscriber\Log\Formatter::'.$format);
         }
 
         $subscriber = new LogSubscriber($logger, $format);