[AUTOMATED] Update terraform-null-label versions to support Terraform 0.13 (#16)

* [AUTOMATED] Update terraform-null-label versions to support Terraform 0.13

* Updated README.md

Co-authored-by: actions-bot <[email protected]>

Author: Gowiem

main.tf

@@ -1,5 +1,5 @@
 module "label" {
-  source      = "git::https://github.com/cloudposse/terraform-null-label.git?ref=tags/0.16.0"
+  source      = "git::https://github.com/cloudposse/terraform-null-label.git?ref=tags/0.17.0"
   namespace   = var.namespace
   stage       = var.stage
   environment = var.environment