Fix alfy-init freezing with some editors (e.g. vim)

[gil]

Hey folks!

When you have a config.json file in your project, during installation alfy-init is gonna call alfred-config to copy this file and open on the default editor.

There's a problem when you have a terminal-based editor such as vim set, postinstall script is gonna freeze waiting for the editor to close, but it's never visible for the user in the first place, so you'll be stuck.

This PR tries to fix this issue by inheriting stdio.

If you wanna try to reproduce this, simply create a config.json file in your alfy project, run EDITOR=vim npm install and you should be stuck as well.