Fix loader.php path

Author: thinkingserious

README.md

@@ -81,9 +81,9 @@ And add to `loader.php` code below:
 ```php
 <?php
 
-require_once __DIR__ . '/php-http-client/lib/Client.php';
-require_once __DIR__ . '/php-http-client/lib/Response.php';
-require_once __DIR__ . '/sendgrid-php/lib/SendGrid.php';
+require_once __DIR__ . '/lib/php-http-client/lib/Client.php';
+require_once __DIR__ . '/lib/php-http-client/lib/Response.php';
+require_once __DIR__ . '/lib/sendgrid-php/lib/SendGrid.php';
 
 ```