Update README.md

[adrianvu]

Previously had an error connection refused. Fix "-p 8080:80" to "-p 80:80". Port 80 instead of 8080 was exposed in Dockerfile. Now it should work when trying to access from outside the container.

[bylexus]

I do not agree: The documentation is meant to show how to map another Host's port to the internal port 80. This is common practice if you have multiple containers running on the same host. Of course you CAN map it to the host's standard port 80, but you don't have to.