Update ExtAuthComponent.php

It seem like Router::Url('/') already return the trailing slash for the base url. This code make it so that there are 2 slash http://example.com//call_back.

Author: mchiron

Controller/Component/ExtAuthComponent.php

@@ -47,7 +47,7 @@ public function __construct(ComponentCollection $collection, array $settings = a
 		$this->settings = array_merge($this->settings, array(
 
 			// Default Settings
-			'callbackURL'                   => Router::url('/', true).'/auth_callback/{PROVIDER}',
+			'callbackURL'                   => Router::url('/', true).'auth_callback/{PROVIDER}',
 			'sessionVariableRequestToken'   => 'request_token',
 			'sessionVariableAccessToken'    => 'access_token',