changed it to execute recipes on all instances in a layer

The stack looks like this:
![screen shot 2014-09-11 at 11 01 57 am](https://cloud.githubusercontent.com/assets/2453875/4237208/05d9a21e-39cd-11e4-9bc3-21623ac00f6f.png)


First command: `bundle exec bin/opsicle execute-recipes staging -r sportngin-platform::list-attributes -l main-utility` 
Second command: `bundle exec bin/opsicle execute-recipes staging -r sportngin-platform::list-attributes -l main-utility,rails-puma-app`

deployments looks like:

![screen shot 2014-09-11 at 11 01 42 am](https://cloud.githubusercontent.com/assets/2453875/4237238/3af68a8e-39cd-11e4-9800-291f01bb4ec2.png)

As you can see the first command ran on only 1 instance (the main utility layer), the second command ran on 3 instances (main-utility + rails-app)


@elliothursh real quick, can you add one more test here that makes sure that if only one layer (out of many) is provided, that only the instance id's from that will be returned.

For example, if you were to change the code for `instance_ids` to be this:

```ruby
get_info.map{ |layer| layer.get_instance_ids }.flatten.compact.uniq
```

The current tests would still pass (I think).