[doc] fixes typo

more here: Payum/Payum#455 (comment)

Author: makasim

Resources/docs/get-it-started.md

@@ -27,7 +27,7 @@ use Payum\Core\Payum;
 /** @var Payum $payum */
 $payum = (new PayumBuilder())
     ->addDefaultStorages()
-    ->addGatewayConfig('gatewayName', [
+    ->addGateway('gatewayName', [
         'factory' => 'offline'
     ])
 

Tests/Action/StatusActionTest.php

@@ -146,7 +146,7 @@ public function shouldMarkCanceledIfStatusSetToCanceled()
         $request = new GetBinaryStatus(array(
             Constants::FIELD_STATUS => Constants::STATUS_CANCELED,
         ));
-        $request->markCanceled();
+        $request->markUnknown();
 
         $action = new StatusAction();