Add required imports to example code in README.md
Add required imports to example code in README.md

Signed-off-by: Thomas Leonard <ea62ade398c3addd3bcc52285a00e98f3b0c618f@docker.com>

mahak/libnetwork,mahak/libnetwork,mahak/libnetwork,medallia/libnetwork,docker/libnetwork,medallia/libnetwork,docker/libnetwork,docker/libnetwork,medallia/libnetwork