Allow whole config directories under ~ 

I asked a question on closed issue https://github.com/freshshell/fresh/issues/19#issuecomment-12121921, and having investigated it a bit more, I think it might be a new issue.
Work-round appears to be:
```bash
fresh mutt/muttrc --file=~/.mutt/muttrc
fresh mutt/colours --file=~/.mutt/colours
```
But I'd prefer to have the whole dir handled in one line (in case I forget to add one of the files)