chore: override the versioning section in the README (#255)

.readme-partials.yaml

@@ -118,4 +118,9 @@ custom_content: |
   - [`StorageExample`](https://github.com/googleapis/google-cloud-java/tree/master/google-cloud-examples/src/main/java/com/google/cloud/examples/storage/StorageExample.java) is a simple command line interface that provides some of Cloud Storage's functionality.  Read more about using the application on the [`StorageExample` docs page](https://github.com/googleapis/google-cloud-java/blob/master/google-cloud-examples/README.md).
   - [`Bookshelf`](https://github.com/GoogleCloudPlatform/getting-started-java/tree/master/bookshelf) - An App Engine application that manages a virtual bookshelf.
     - This app uses `google-cloud` to interface with Cloud Datastore and Cloud Storage. It also uses Cloud SQL, another Google Cloud Platform service.
-  - [`Flexible Environment/Storage example`](https://github.com/GoogleCloudPlatform/java-docs-samples/tree/master/flexible/cloudstorage) - An app that uploads files to a public Cloud Storage bucket on the App Engine Flexible Environment runtime.
+  - [`Flexible Environment/Storage example`](https://github.com/GoogleCloudPlatform/java-docs-samples/tree/master/flexible/cloudstorage) - An app that uploads files to a public Cloud Storage bucket on the App Engine Flexible Environment runtime.
+
+versioning: |
+  This library follows [Semantic Versioning](http://semver.org/), but does update [Storage interface](src/main/java/com.google.cloud.storage/Storage.java)
+  to introduce new methods which can break your implementations if you implement this interface for testing purposes.
+