Nginx - Path based

nginx.conf
....
        location /OliveTin/ {
                proxy_pass http://localhost:1337/;
                proxy_redirect http://localhost:1337/ http://localhost/OliveTin/;
        }
....

Note, because you are changing the default path (from / to /OliveTin/), you will need to tell the OliveTin webUI where to find the API.

You need to also set externalRestAddress in your config.yaml like this;

OliveTin config.yaml
externalRestAddress: http://myserver/OliveTin