Merge pull request #65 from Jhut89/3.1.1

fix broken ID check

Author: Jhut89

src/Resources/Lists.php

@@ -50,8 +50,7 @@ public function __construct(MailchimpRequest $request, MailchimpSettings $settin
      */
     public function batchSubscribe($members = [], $update_existing = false)
     {
-
-        $this->throwIfNot("id", $this->subclass_resource);
+        $this->throwIfNot("id", $this->list_id);
         $params = [
             'members' => $members,
             'update_existing' => $update_existing