Authentication with AUTH_URL_TOKEN bug fix

If user authenticates with AUTH_URL_TOKEN and request parameter are not empty access_token must be appended by `&` (and not `?`)

Author: matejskubic

lib/Github/HttpClient/Listener/AuthListener.php

@@ -86,7 +86,7 @@ public function preSend(RequestInterface $request)
                 }
 
                 $url  = $request->getUrl();
-                $url .= '?'.utf8_encode(http_build_query(array('access_token' => $this->options['tokenOrLogin']), '', '&'));
+                $url .= (false === strpos($url, '?') ? '?' : '&').utf8_encode(http_build_query(array('access_token' => $this->options['tokenOrLogin']), '', '&'));
 
                 $request->fromUrl(new Url($url));
                 break;