Copyedit builds

Trying again since the first PR seems to have been lost.

Docker-DCO-1.1-Signed-off-by: Fred Lifton fred.lifton@docker.com (github: fredlf)
All "README.md"s should be marked/written the same way, I believe.
Previously it was: `README.md` (marked as code).
However, here it is left *plain*.