.zsh: remove useless comment
.zsh: remove debug 'echo' mistakenly committed
.zsh: add docker-cleanup function, inspired by http://kartar.net/2014/03/some-useful-docker-bash-functions-and-aliases/
.zsh: add docker-ipaddress function, inspired by http://kartar.net/2014/03/some-useful-docker-bash-functions-and-aliases/
.zsh: fix functions that were precedently aliases and needed arguments