Simple deploy issue 143

This is to address simple deploy issue https://github.com/intuit/simple_deploy/issues/143 where inconsistent results are being returned when using simple deploy to list the instances. Changed the overall method by doing a query on cloud formation to return the auto scale group, then query the auto scale group to list all the instances.

Not implemented just yet is the next token which will be needed if the number of instances exceeds 50.