0.25.0 Make `instance_count` independent of `autoscaling_min_capacity`

what

• Make instance_count independent of autoscaling_min_capacity

why

Fix for #63

The cluster_size or the instance_count should be independent of autoscaling_min_capacity as autoscaling_min_capacity is automatically taken care of by AWS through the autoscaling policy.

For example, when autoscaling is enabled:

if I specify:

    cluster_size = 2
    autoscaling_min_capacity = 1

terraform creates only one instance even though cluster_size is set to 2 ,

and if I specify:

    cluster_size = 2
    autoscaling_min_capacity = 2 

terraform spins up 2 instances but AWS autoscaling policy immediately spins up one more instance, which is not desired.