Update instructions about master branch vs released changes

Author: clareliguori

README.md

@@ -2,10 +2,9 @@
 
 This repository holds Dockerfiles of official AWS CodeBuild curated Docker images. Please refer to [the AWS CodeBuild User Guide](http://docs.aws.amazon.com/codebuild/latest/userguide/build-env-ref.html) for list of environments supported by AWS CodeBuild.
 
-Branch|Build
----|---
-master|![Build Status](https://codebuild.us-west-2.amazonaws.com/badges?uuid=eyJlbmNyeXB0ZWREYXRhIjoiSkJibVVQVEpvUms1cmw3YVlnU1hSdkpBQ0c5SFgyTkJXMFBFdEU2SWtySHREcUlUVlRhbW4zMEd3NlhsOWIzUWgvRkxhUWVSSTFPZGNNakNHRVNLalY0PSIsIml2UGFyYW1ldGVyU3BlYyI6IlV0QjBRZXRvS0F5dE5vbTciLCJtYXRlcmlhbFNldFNlcmlhbCI6MX0%3D&branch=master)
-release|![Build Status](https://codebuild.us-west-2.amazonaws.com/badges?uuid=eyJlbmNyeXB0ZWREYXRhIjoiSkJibVVQVEpvUms1cmw3YVlnU1hSdkpBQ0c5SFgyTkJXMFBFdEU2SWtySHREcUlUVlRhbW4zMEd3NlhsOWIzUWgvRkxhUWVSSTFPZGNNakNHRVNLalY0PSIsIml2UGFyYW1ldGVyU3BlYyI6IlV0QjBRZXRvS0F5dE5vbTciLCJtYXRlcmlhbFNldFNlcmlhbCI6MX0%3D&branch=release)
+![Build Status](https://codebuild.us-west-2.amazonaws.com/badges?uuid=eyJlbmNyeXB0ZWREYXRhIjoiSkJibVVQVEpvUms1cmw3YVlnU1hSdkpBQ0c5SFgyTkJXMFBFdEU2SWtySHREcUlUVlRhbW4zMEd3NlhsOWIzUWgvRkxhUWVSSTFPZGNNakNHRVNLalY0PSIsIml2UGFyYW1ldGVyU3BlYyI6IlV0QjBRZXRvS0F5dE5vbTciLCJtYXRlcmlhbFNldFNlcmlhbCI6MX0%3D&branch=master)
+
+The master branch will sometimes have changes that are still in the process of being released in AWS CodeBuild.  See the latest released versions of the Dockerfiles ![here](https://github.com/aws/aws-codebuild-docker-images/releases).
 
 ### How to build Docker images