add an image to show the use of the Docker OSX applet

Docker-DCO-1.1-Signed-off-by: Sven Dowideit <SvenDowideit@docker.com> (github: SvenDowideit)
Merge pull request #6264 from SvenDowideit/add-osx-boot2docker-start

add an image to show the use of the Docker OSX applet