[AIRFLOW-208] Add badge to show supported Python versions
diff --git a/README.md b/README.md
index e911225aeee2f..211d9844d1890 100644
--- a/README.md
+++ b/README.md
@@ -5,6 +5,7 @@
 [![Coverage Status](https://img.shields.io/codecov/c/github/apache/incubator-airflow/master.svg)](https://codecov.io/github/apache/incubator-airflow?branch=master)
 [![Documentation Status](https://readthedocs.org/projects/airflow/badge/?version=latest)](https://airflow.readthedocs.io/en/latest/?badge=latest)
 [![License](http://img.shields.io/:license-Apache%202-blue.svg)](http://www.apache.org/licenses/LICENSE-2.0.txt)
+[![PyPI - Python Version](https://img.shields.io/pypi/pyversions/apache-airflow.svg)](https://pypi.org/project/apache-airflow/)
 [![Join the chat at https://gitter.im/apache/incubator-airflow](https://badges.gitter.im/apache/incubator-airflow.svg)](https://gitter.im/apache/incubator-airflow?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge)
 
 _NOTE: The transition from 1.8.0 (or before) to 1.8.1 (or after) requires uninstalling Airflow before installing the new version. The package name was changed from `airflow` to `apache-airflow` as of version 1.8.1._

Make sure you have checked _all_ steps below.

### Jira

- [x] My PR addresses the following [Airflow Jira](https://issues.apache.org/jira/browse/AIRFLOW/) issues and references them in the PR title. For example, "\[AIRFLOW-XXX\] My Airflow PR"
  - https://issues.apache.org/jira/browse/AIRFLOW-208
  - In case you are fixing a typo in the documentation you can prepend your commit with \[AIRFLOW-XXX\], code changes always need a Jira issue.

### Description

- [x] Here are some details about my PR, including screenshots of any UI changes:
Add badge to show supported Python versions

### Tests

- [x] My PR adds the following unit tests __OR__ does not need testing for this extremely good reason:

### Commits

- [x] My commits all reference Jira issues in their subject lines, and I have squashed multiple commits if they address the same issue. In addition, my commits follow the guidelines from "[How to write a good git commit message](http://chris.beams.io/posts/git-commit/)":
  1. Subject is separated from body by a blank line
  1. Subject is limited to 50 characters (not including Jira issue reference)
  1. Subject does not end with a period
  1. Subject uses the imperative mood ("add", not "adding")
  1. Body wraps at 72 characters
  1. Body explains "what" and "why", not "how"

### Documentation

- [x] In case of new functionality, my PR adds documentation that describes how to use it.
  - When adding new operators/hooks/sensors, the autoclass documentation generation needs to be added.

### Code Quality

- [x] Passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
