Return exit code 1 when migration is cancelled (#49)

Author: Einar

src/Console/MigrateCommand.php

@@ -101,7 +101,7 @@ protected function handleExecutedUnavailableMigrationsException(
 
         if (!$this->confirm('Are you sure you wish to continue?')) {
             $this->error('Migration cancelled!');
-            die;
+            exit(1);
         }
     }
 }