Fixed some typos and other issues from ostezer comments.

Docker-DCO-1.1-Signed-off-by: William Henry <whenry@redhat.com> (github: ipbabble)

 Changes to be committed:
	modified:   contrib/man/md/docker-build.1.md
	modified:   contrib/man/md/docker-run.1.md
	modified:   contrib/man/md/docker-tag.1.md