Add python3statement.org badges to README
.. image:: https://img.shields.io/pypi/v/cherrypy.svg
:target: https://pypi.org/project/cherrypy
+.. image:: https://img.shields.io/badge/Python%203%20only-pip%20install%20%22%3E%3D18.0.0%22-%234da45e.svg
+ :target: https://python3statement.org/
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+.. image:: https://img.shields.io/badge/Python%203%20and%202-pip%20install%20%22%3C18.0.0%22-%2349a7e9.svg
+ :target: https://python3statement.org/#sections40-timeline
+
+
+
.. image:: https://readthedocs.org/projects/cherrypy/badge/?version=latest
:target: https://docs.cherrypy.org/en/latest/?badge=latest
