feature(core): command fix

@grola FYI

src/ActivationReminder/Composer/PrepareActivationReminderCommand.php

@@ -3,6 +3,7 @@
 namespace WPDesk\ActivationReminder\Composer;
 
 use Composer\Command\BaseCommand;
+use Symfony\Component\Console\Command\Command;
 use Symfony\Component\Console\Input\InputInterface;
 use Symfony\Component\Console\Output\OutputInterface;
 
@@ -58,6 +59,8 @@ class PrepareActivationReminderCommand extends BaseCommand
 	    $this->regenerate_autoload( $target_file, $input );
 
 	    $output->writeln( "Activation reminder created." );
+
+		return Command::SUCCESS;
     }
 
     private function create_or_get_target_file_name( array $class_map, $random_class, $random_letter ) {