Add CircleCI badge

Author: snemetz

README.md

@@ -1,3 +1,5 @@
+[![CircleCI](https://circleci.com/gh/devops-workflow/terraform-aws-autoscaling/tree/master.svg?style=svg)](https://circleci.com/gh/devops-workflow/terraform-aws-autoscaling/tree/master)
+
 AWS Auto Scaling Group (ASG) Terraform module
 ================================================
 
@@ -97,4 +99,4 @@ Module managed by [Anton Babenko](https://github.com/antonbabenko).
 License
 -------
 
-Apache 2 Licensed. See LICENSE for full details.
+Apache 2 Licensed. See LICENSE for full details.