use id_ to reference state ID

Salt makes a distinction between state ID and name, although by default the ID is used as the name. This pull request preserves that, allowing for use of the 'name' and 'names' kwargs. This is useful for avoiding ID clashes.

```python
Service.running('stopped-services', names=['nginx', 'foo'])

for service in ['cron', 'httpd']:
    with Pkg.installed('{0}-package'.format(service), name=service):
        Service.running(service)
```