docs(readme): Added CLA Assistant badge

Author: mediumTaj

README.md

@@ -4,6 +4,7 @@
 [![Slack](https://wdc-slack-inviter.mybluemix.net/badge.svg)](https://wdc-slack-inviter.mybluemix.net)
 [![codecov.io](https://codecov.io/github/watson-developer-cloud/python-sdk/coverage.svg?branch=master)](https://codecov.io/github/watson-developer-cloud/python-sdk?branch=master)
 [![Latest Stable Version](https://img.shields.io/pypi/v/watson-developer-cloud.svg)](https://pypi.python.org/pypi/watson-developer-cloud)
+[![CLA assistant](https://cla-assistant.io/readme/badge/watson-developer-cloud/python-sdk)](https://cla-assistant.io/watson-developer-cloud/python-sdk)
 
 Python client library to quickly get started with the various [Watson APIs][wdc] services.