Add asg_id output (#41)

Author: spikeheap

README.md

@@ -36,6 +36,7 @@ Only SSH access is allowed to the bastion host.
 
   * ssh_user - SSH user to login to bastion
   * security_group_id - ID of the security group the bastion host is launched in.
+  * asg_id - The ID of the AutoScalingGroup the bastion host is launched within. 
 
 ## Example:
 

outputs.tf

@@ -5,3 +5,7 @@ output "ssh_user" {
 output "security_group_id" {
   value = "${aws_security_group.bastion.id}"
 }
+
+output "asg_id" {
+  value = "${aws_autoscaling_group.bastion.id}"
+}