Making localhost accessible outside LAN

Question

I have a RPi running nginx as a web-server (default installation except /var/www as default directory), but I can only access it inside LAN.

I followed this tutorial and in sites-available I created a file with the following code:

server {
 listen 80;
 root /var/www;
 index index.php index.html index.htm;

 location ~ \.php$ {
  fastcgi_pass unix:/var/run/php5-fpm-sock;
  fastcgi_index index.php;
  include fastcgi_params;
 }
}

What do I need to do to make it accessible from outside my network?