Added EBS snapshot changes

@mmell 
https://trello.com/c/XDCFeDX2/75-cnc-should-perform-ebs-snapshots
@cjawale `if instance_names != nil` is not necessary if the signature is this: 
    
    create_snapshot_from_instance_name(region, instance_names = [], namespace = '')

Please apply the same to all of the methods on this page.