Ensuring all arguments are strings

Author: davidgrayston

src/Formatter/Formatter.php

@@ -307,7 +307,7 @@ public function onAfterStepTested(BehatEvent\AfterStepTested $event)
         $arguments = [];
         foreach ($result->getSearchResult()->getMatchedArguments() as $argument) {
             $a = new \stdClass();
-            $a->val = $argument;
+            $a->val = (string) $argument;
             $arguments[] = $a;
         }
         if ($arguments) {