Just a couple of files to deploy manually a nice maintenance mode for wordpress.
Learn more about this repo on our blog: http://inside.agentslug.com/knowledge-base/coding-tips/tutorial-for-custom-maintenance-mode-in-wordpress
Repo has two files: .maintenance, and maintenance.php. The php file job is to compile a maintenance mode view. The .maintenance file (which, is actually also a php file) turning on the maintenance mode if exists in your wordpress main directory.