allow key for consistency

Author: taylorotwell

src/Illuminate/Mail/MailManager.php

@@ -371,6 +371,7 @@ protected function createPostmarkTransport(array $config)
             'postmark+api',
             'default',
             $config['token']
+                ?? $config['key']
                 ?? $this->app['config']->get('services.postmark.token')
                 ?? $this->app['config']->get('services.postmark.key'),
             null,