Add an initial nginx configuration

Initial nginx.conf thanks to [VVV](http://github.com/10up/varying-vagrant-vagrants) project.

Also adds a user/group of www-data:www-data for the nginx process to run as.
Add default server handling for nginx

Accounts for a default server for the time being that serves files from /var/www/.

iptables still blocks port 80 by default, so we'll need to address that next.