documentation change
documentation change

Signed-off-by: Anda Xu <d8873ed76b30aa5393b138ce11b4db169d7db492@docker.com>

vdemeester/docker-py,vpetersson/docker-py,dimaspivak/docker-py,vdemeester/docker-py,kaiyou/docker-py,youhong316/docker-py,youhong316/docker-py,docker/docker-py,kaiyou/docker-py,funkyfuture/docker-py,docker/docker-py,vpetersson/docker-py,dimaspivak/docker-py,funkyfuture/docker-py