Edits and fixes based on review.

Docker-DCO-1.1-Signed-off-by: Fred Lifton <fred.lifton@docker.com> (github: fredlf)
While I agree with Fred that this is definitely a word that's in very, very
common use with our target audience for this particular document, I'd be
very interested to hear your suggestions for a replacement, because I don't
know that it's really worth arguing about unless we actually have an
alternative, is it?