aws-v4.0.0

48b588d add autoscaling_group_id and autoscaling_group_arn outputs (#61)
ec09a27 make route53_zone_id optional (#62)
d5c2a0d make userdata exit with code 0 when no reboot is required (#67)
f851e65 add ssh_key_name input to use a aws_key_pair resource provided by user (#60)
fcd8c59 add additional_user_data_end input (#63)