Allow to pass any arguments to z

before:

```
$ z --help
12         /Users/Jean/Dropbox
12         /Users/Jean/work

$ z work
/Users/Jean/work
```

after:

```
z --help
z [-chlrtx] args

$ z work
/Users/Jean/work
```
Merge pull request #228 from JeanMertz/patch-1

Allow to pass any arguments to z