ZSH completion #6

I think it might be a good idea to enhance the bash completion with some ZSH completion file.

Here is what have been already done in oh-my-zsh : https://github.com/miklos-martin/oh-my-zsh-plugins/blob/master/nginx/

I'm a fervent user of nginx_{en,dis}site, I'd appreciate ! (If I have time and if I learn some ZSH-scripts basics, I'll try to translate your script, but I don't feel confident about it.)