Added the Elastic IP addresses for the Nat gateways to the outputs

main.tf

@@ -151,3 +151,7 @@ output "public_route_table_id" {
 output "private_route_table_ids" {
   value = ["${aws_route_table.private.*.id}"]
 }
+
+output "nat_gateway_public_ips" {
+  value = ["${aws_eip.nat.*.public_ip}"]
+}