chore: add build badges to README (GoogleCloudPlatform#3689)

fixes GoogleCloudPlatform#3556

Author: Takashi Matsuo

README.md

@@ -7,8 +7,19 @@
 
 This repository holds the samples used in the python documentation on [cloud.google.com](https://cloud.google.com).
 
-[![Build Status](https://travis-ci.org/GoogleCloudPlatform/python-docs-samples.svg)](https://travis-ci.org/GoogleCloudPlatform/python-docs-samples)
-[![Coverage Status](https://coveralls.io/repos/github/GoogleCloudPlatform/python-docs-samples/badge.svg?branch=HEAD)](https://coveralls.io/github/GoogleCloudPlatform/python-docs-samples?branch=HEAD)
+[![Build Status][py-2.7-shield]][py-2.7-link]
+[![Build Status][py-3.6-shield]][py-3.6-link]
+[![Build Status][py-3.7-shield]][py-3.7-link]
+[![Build Status][py-3.8-shield]][py-3.8-link]
+
+[py-2.7-shield]: https://storage.googleapis.com/cloud-devrel-public/python-docs-samples/badges/py-2.7.svg
+[py-2.7-link]: https://storage.googleapis.com/cloud-devrel-public/python-docs-samples/badges/py-2.7.html
+[py-3.6-shield]: https://storage.googleapis.com/cloud-devrel-public/python-docs-samples/badges/py-3.6.svg
+[py-3.6-link]: https://storage.googleapis.com/cloud-devrel-public/python-docs-samples/badges/py-3.6.html
+[py-3.7-shield]: https://storage.googleapis.com/cloud-devrel-public/python-docs-samples/badges/py-3.7.svg
+[py-3.7-link]: https://storage.googleapis.com/cloud-devrel-public/python-docs-samples/badges/py-3.7.html
+[py-3.8-shield]: https://storage.googleapis.com/cloud-devrel-public/python-docs-samples/badges/py-3.8.svg
+[py-3.8-link]: https://storage.googleapis.com/cloud-devrel-public/python-docs-samples/badges/py-3.8.html
 
 For a more detailed introduction to a product, check the README.md in the
 corresponding folder.