Add minimum-stability => dev to test composer.json.

Author: greg-1-anderson

composer.lock

@@ -134,6 +134,7 @@ protected function composerJSONDefaults() {
       'scripts' => array(
         'drupal-scaffold' =>  'DrupalComposer\\DrupalScaffold\\Plugin::scaffold'
       ),
+      'minimum-stability' => 'dev',
     );
   }