docs: add concrete example to readme

Author: Qingping Hou

README.md

@@ -23,8 +23,8 @@ module "datadog" {
   source                = "git::https://github.com/scribd/terraform-aws-datadog.git?ref=master"
   aws_account_id        = data.aws_caller_identity.current.account_id
   datadog_api_key       = var.datadog_api_key
-  env                   = local.tags.env
-  namespace             = local.tags.namespace
+  env                   = "prod"
+  namespace             = "team_foo"
 
   cloudtrail_bucket_id  = aws_s3_bucket.org-cloudtrail-bucket.id
   cloudtrail_bucket_arn = aws_s3_bucket.org-cloudtrail-bucket.arn
@@ -52,8 +52,8 @@ module "datadog" {
   datadog_api_key                = var.datadog_api_key
   create_elb_logs_bucket         = false
   enable_datadog_aws_integration = false
-  env                            = local.tags.env
-  namespace                      = local.tags.namespace
+  env                            = "prod"
+  namespace                      = "project_foo"
 
   cloudwatch_log_groups = ["cloudwatch_log_group_1", "cloudwatch_log_group_2"]
 }