Fix single directory in namespace

As suggested here the second issue and a pull request to the directory thingy.

```
(fakir-fake-file
    (list
     (fakir-file
      :filename "blah"
      :directory "/home/fakir-test"
      :content "blah!")
     (fakir-file
      :filename "blah2"
      :directory "/home/fakir-test"
      :content "blah2!")
     (fakir-file
      :filename "blah3"
      :directory "/home/fakir-test"
      :content "NO WAY!")
     (fakir-file
      :filename "blah3"
      :directory "/tmp"
      :content "totally testing!"))
  (let ((real-home-dir
         (file-name-as-directory (getenv "HOME"))))
    (kvhash->alist fakir-file-namespace)))

=>

(("/tmp/blah3" . [cl-struct-fakir-file "blah3" "/tmp" "totally testing!" "Mon, Feb 27 2012 22:10:19 GMT"]) 
("/home/fakir-test/blah3" . [cl-struct-fakir-file "blah3" "/home/fakir-test" "NO WAY!" "Mon, Feb 27 2012 22:10:19 GMT"]) 
("/home/fakir-test/blah2" . [cl-struct-fakir-file "blah2" "/home/fakir-test" "blah2!" "Mon, Feb 27 2012 22:10:19 GMT"]) 
("/home/fakir-test/" . [cl-struct-fakir-file "blah" "/home/fakir-test" "blah!" "Mon, Feb 27 2012 22:10:19 GMT"]) 
("/home/fakir-test/blah" . [cl-struct-fakir-file "blah" "/home/fakir-test" "blah!" "Mon, Feb 27 2012 22:10:19 GMT"]))
```

The question I posed was, why there is only one "/home/fakir-test/" directory.
The reason of my confusion was at this line:
https://github.com/nicferrier/emacs-fakir/blob/master/fakir.el#L475

I rewrote it a little to recursively add faked files for the parent directories without `:content`.

The result now looks like this:

```
(("/tmp" . [cl-struct-fakir-file "tmp" "/" "" "Mon, Feb 27 2012 22:10:19 GMT"])
 ("/tmp/blah3" . [cl-struct-fakir-file "blah3" "/tmp" "totally testing!" "Mon, Feb 27 2012 22:10:19 GMT"])
 ("/home/fakir-test/blah3" . [cl-struct-fakir-file "blah3" "/home/fakir-test" "NO WAY!" "Mon, Feb 27 2012 22:10:19 GMT"])
 ("/home/fakir-test/blah2" . [cl-struct-fakir-file "blah2" "/home/fakir-test" "blah2!" "Mon, Feb 27 2012 22:10:19 GMT"])
 ("/" . [cl-struct-fakir-file "" "/" "" "Mon, Feb 27 2012 22:10:19 GMT"])
 ("/home" . [cl-struct-fakir-file "home" "/" "" "Mon, Feb 27 2012 22:10:19 GMT"])
 ("/home/fakir-test" . [cl-struct-fakir-file "fakir-test" "/home/" "" "Mon, Feb 27 2012 22:10:19 GMT"])
 ("/home/fakir-test/blah" . [cl-struct-fakir-file "blah" "/home/fakir-test" "blah!" "Mon, Feb 27 2012 22:10:19 GMT"]))
```

I am not quite sure about the root directory yet.

Next step would be to add a `:directory-p` flag. :+1: