Allow Z to help with tab completion anywhere

[inducer]

It'd be neat if you could devise a scheme allowing Z to help with tab completion of directories as arguments to any command.

[langston-barrett]

zsh and bash do this completely differently, of course.

[mrjohannchang]

I've also added the tab completion for z with fzf. Check it out: https://github.com/changyuheng/fz