Add attribution to @ronlut in README

Author: tiangolo

README.md

@@ -739,6 +739,10 @@ You will see your Flask debugging server start, you will see how it sends respon
 
 2018-06-22:
 
+* You can now use `NGINX_WORKER_CONNECTIONS` to set the maximum number of Nginx worker connections and `NGINX_WORKER_OPEN_FILES` to set the maximum number of open files. Thanks to [ronlut](https://github.com/ronlut) in [this PR](https://github.com/tiangolo/uwsgi-nginx-flask-docker/pull/56).
+
+2018-06-22:
+
 Improvements from parent image:
 
 * Make uWSGI require an app to run, instead of going in "full dynamic mode" while there was an error. Supervisord doesn't terminate itself but tries to restart uWSGI and shows the errors. Uses `need-app` as suggested by [luckydonald](https://github.com/luckydonald) in [this comment](https://github.com/tiangolo/uwsgi-nginx-flask-docker/issues/3#issuecomment-321991279).