README: add Vagrant filesystem notes
README: add Vagrant filesystem notes

phusion/passenger_apt_automation,LoveMondays/passenger_apt_automation,shaneog/passenger_apt_automation,LoveMondays/passenger_apt_automation,phusion/passenger_apt_automation,LoveMondays/passenger_apt_automation,LoveMondays/passenger_apt_automation,phusion/passenger_apt_automation,LoveMondays/passenger_apt_automation,shaneog/passenger_apt_automation,shaneog/passenger_apt_automation,shaneog/passenger_apt_automation,shaneog/passenger_apt_automation,LoveMondays/passenger_apt_automation,shaneog/passenger_apt_automation,LoveMondays/passenger_apt_automation,LoveMondays/passenger_apt_automation,shaneog/passenger_apt_automation,phusion/passenger_apt_automation,phusion/passenger_apt_automation,LoveMondays/passenger_apt_automation,phusion/passenger_apt_automation,phusion/passenger_apt_automation,shaneog/passenger_apt_automation,shaneog/passenger_apt_automation