lets talk about the other way to make base images

Docker-DCO-1.1-Signed-off-by: Sven Dowideit <SvenDowideit@home.org.au> (github: SvenDowideit)
Fix misspelling

Docker-DCO-1.1-Signed-off-by: Adrian Mouat <adrian@adrianmouat.com> (github: amouat)
Merge pull request #4252 from SvenDowideit/mention-scratch-image

lets talk about the other way to make base images
Merge pull request #4261 from amouat/patch-1

Fix misspelling
Merge branch 'master' of https://github.com/dotcloud/docker