Update readme badges and CI notes

Author: grantjenks

README.rst

@@ -77,16 +77,16 @@ Features
 - Thread-safe and process-safe
 - Supports multiple eviction policies (LRU and LFU included)
 - Keys support "tag" metadata and eviction
-- Developed on Python 3.8
-- Tested on CPython 3.5, 3.6, 3.7, 3.8
+- Developed on Python 3.9
+- Tested on CPython 3.6, 3.7, 3.8, 3.9
 - Tested on Linux, Mac OS X, and Windows
-- Tested using Travis CI and AppVeyor CI
+- Tested using GitHub Actions
 
-.. image:: https://api.travis-ci.org/grantjenks/python-diskcache.svg?branch=master
-    :target: http://www.grantjenks.com/docs/diskcache/
+.. image:: https://github.com/grantjenks/python-diskcache/workflows/integration/badge.svg
+   :target: https://github.com/grantjenks/python-diskcache/actions?query=workflow%3Aintegration
 
-.. image:: https://ci.appveyor.com/api/projects/status/github/grantjenks/python-diskcache?branch=master&svg=true
-    :target: http://www.grantjenks.com/docs/diskcache/
+.. image:: https://github.com/grantjenks/python-diskcache/workflows/release/badge.svg
+   :target: https://github.com/grantjenks/python-diskcache/actions?query=workflow%3Arelease
 
 Quickstart
 ----------