initial formation for zookeeper

not ready to merge, just for comparison. 
```python
launchconf = atlas.instance_launchconf(
    	template,
    	"ZK",
    	Metadata=i_meta_data,
    	SecurityGroups=[Ref(zk_secgrp)],
)
```

and then an autoscaling group

```python
scaling_group = atlas.instance_scalegrp(
    template,
    'ZK',
    LaunchConfigurationName=Ref(launchconf),
    MinSize=Ref('MinSize'),
    MaxSize=Ref('MaxSize'),
    DesiredCapacity=Ref('DesiredCapacity'),
)
```