README: drop travis badge
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py3status
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-|travis| |readthedocs|
+|CI| |readthedocs|
.. |CI| image:: https://github.com/ultrabug/py3status/workflows/CI/badge.svg
-.. |travis| image:: https://travis-ci.org/ultrabug/py3status.svg?branch=master
.. |readthedocs| image:: https://readthedocs.org/projects/py3status/badge/?version=latest
**py3status** is an extensible i3status wrapper written in python.
