Fix zypper

`states/pkgrepo.py` always sets 'ppa_auth' when calling `get_repo()`. For `modules/zypper.py` this results in an error. The pull request fixes this problem on the `modules/zypper.py` side by ignoring the extra argument.

sample SLS:
```yaml
jenkins:
    pkgrepo.managed: 
        - url: http://download.opensuse.org/repositories/devel:/tools:/building/openSUSE_13.1/
        - name: devel:tools:building.repo
        - gpgcheck: 0
        - require_in:
            - pkg: jenkins
    pkg.installed:
        - name: jenkins
```

Second change is the specification of 'six' as a requirement (introduced through `modules/zypper.py`).