Add grunt task for Heroku deploy
Revert "Add grunt task for Heroku deploy"

This reverts commit eeb0aba8e41e280b922b9b812879fb5b51f36011.
Install grunt-cli to run on remote server
Add Grunt as postinstall command to run
Add production environment in docpad
Build optimized website into out-dev directory
No need to run grunt when npm finishes installing packages