Remove references to python 3.5 in README

Author: davesque

README.rst

@@ -519,13 +519,13 @@ directory:
 
 .. code-block:: bash
 
+  pyenv install 3.8.x
   pyenv install 3.7.x
   pyenv install 3.6.x
-  pyenv install 3.5.x
   cat > .python-version <<EOF
+  3.8.x
   3.7.x
   3.6.x
-  3.5.x
   EOF
 
 Above, the ``x`` in each case should be replaced with the latest corresponding