nginx_unicorn_web_app: Return static maintenance.html with status 503
                       when maintenance_mode file exists.

                       ELB will consider these instances unhealthy.
nginx_unicorn_web_app: add /about location block to handle ELB pings during
                       maintenance mode
nginx_unicorn_web_app: Use static docroot for maintenance checks
nginx_unicorn_web_app: Use static maintenance.html for all requests when
                       in maintenance mode.
maintenance mode: first try at a new cookbook
nginx_unicorn_web_app: add maintenance_mode_on/_off recipes
maintenance_mode_on/_off recipes: looking for docroot opsworks attribute
maintenance_mode_on/_off recipes: still looking for docroot opsworks attribute
maintenance_mode_on/_off recipes: still looking for docroot opsworks attribute
maintenance mode: get rid of separate cookbook for this
maintenance mode: Switch to /etc/maintenance_mode as the flag file, so
                  deploys (which replace docroot) don't automatically
                  take us out of maintenance mode.
nginx_unicorn_web_app: Cover http port 80 as well when returning static
		       maintenance.html with status 503 when
		       maintenance_mode file exists.
Merge pull request #1 from WhitehawkVentures/master-chef-11.4-jay-maintenance-page

master-chef-11.4-jay-maintenance-page