update commands.go
update docker.go
move to pkg
update docs
update name and copyright

Docker-DCO-1.1-Signed-off-by: Victor Vieux <victor.vieux@docker.com> (github: vieux)
change --sinceId to --since-id, update completion and docs

Docker-DCO-1.1-Signed-off-by: Victor Vieux <victor.vieux@docker.com> (github: vieux)