Make requirements checker return error if there were failed checks (yiisoft#196)

Author: maximal

requirements.php

@@ -157,4 +157,6 @@
     );
 }
 
-$requirementsChecker->checkYii()->check($requirements)->render();
+$result = $requirementsChecker->checkYii()->check($requirements)->getResult();
+$requirementsChecker->render();
+exit($result['summary']['errors'] === 0 ? 0 : 1);