Update nginx-proxy to the latest (current version is build from custom branch)

[noisy]

Issue https://github.com/SpisTresci/SpisTresci/issues/12 needed an update of docker-compose to version 2. It was done, however custom version of nginx-proxy was used (https://github.com/SpisTresci/nginx-proxy/).

It seems, that oryginal nginx-proxy should also works after merging nginx-proxy/nginx-proxy#337.

Configuration of project should be updated to used latest version of nginx-proxy.