Improve the shell completion templates
Improve the shell completion templates

* Complete file names when there are no matches.
* Convert to a native Zsh completion script .
* Don't call compinit. That is up to the user. Calling it resets the
completion system.
* Quote array expansion with '@' to avoid dropping empty entries.
* The Zsh completion script can both be eval-ed and installed into
fpath.

alecthomas/kingpin