Update installation_others.rst

root path is normally /var/www. In default environment $server_name/htdocs throws a 404.

inlude fastcgi.conf throws 'open() "/etc/nginx/fastcgi.conf" failed (2: No such file or directory)', assuming fastcgi_params would be correct.

access_log main throws an 'unknown log format "main"', here I don't know how to fix it, so I commented it out for me. Please look into it!

First github-experience for me. If I could do something better please criticize.