get_instance_health

Get a list of instances and their health state.
Example:
```
$ salt myminion boto_elb.get_instance_health my-elb
myminion:
    ----------
    - description:
        N/A
    - instance_id:
        i-1234567e
    - reason_code:
        N/A
    - state:
        InService
    ----------
    - description:
        N/A
    - instance_id:
        i-1234568e
    - reason_code:
        N/A
    - state:
        InService
    ----------
    - description:
        N/A
    - instance_id:
        i-12345675
    - reason_code:
        N/A
    - state:
        InService

```