Fix entry point documentation

README.md

@@ -4,5 +4,5 @@ docker-gunicorn-base
 Base image with [gunicorn](http://gunicorn.org), to run Python web applications.
 The configuration for the app should be copied by sub-images to /etc/gunicorn.conf
 (even though it is a Python file). The name of the application module to run
-should be passed as the $APPLICATION environment variable.
+should be passed as part of the ENTRY\_POINT set by the child image.