Issue terraform-aws-modules#58: Add ElastiCache subnet group name output. (terraform-aws-modules#60)

Author: jekstrom

outputs.tf

@@ -90,6 +90,11 @@ output "elasticache_subnet_group" {
   value       = "${element(concat(aws_elasticache_subnet_group.elasticache.*.id, list("")), 0)}"
 }
 
+output "elasticache_subnet_group_name" {
+  description = "Name of elasticache subnet group"
+  value       = "${element(concat(aws_elasticache_subnet_group.elasticache.*.name, list("")), 0)}"
+}
+
 # Route tables
 output "public_route_table_ids" {
   description = "List of IDs of public route tables"