Added 'sendfile off' to nginx config
because vagrant inherit bug from virtualbox regarding shared folders
in some point it could corrupt files. When you change a file on/in a shared folder,
the change is not seen when through a webserver (e.g. nginx).
for more info: https://github.com/mitchellh/vagrant/issues/351#issuecomment-1339640
ticket at VB: https://www.virtualbox.org/ticket/9069