Add upgrade method

Author: danielbrendel

app/commands/MigrationUpgrade.php

@@ -8,6 +8,13 @@
  * Command handler class
  */
 class MigrationUpgrade implements Asatru\Commands\Command {
+    /**
+     * @return void
+     */
+    public function upgradeTo3dot9()
+    {
+    }
+
     /**
      * @return void
      */