Edits and fixes based on review.

Docker-DCO-1.1-Signed-off-by: Fred Lifton <fred.lifton@docker.com> (github: fredlf)
Yeah, I agree - most readers, especially those who are new to Docker, will assume that `docker run -it official-image bash` or `docker run -it official-image bash -i` will work.  If the official images use `ENTRYPOINT` for something that's not just a wrapper script, then that no longer works, and the beginner now needs to learn about `ENTRYPOINT` and `--entrypoint`.

So maybe I'm misunderstanding the question/confusion here?  It sounds to me like we're in agreement to me.