Improve the release docs with cleaning of pyc files and using twine instead of setup.py upload

doc/release.txt

@@ -57,9 +57,10 @@ Pre-release
    https://github.com/PyCQA/pylint
-Release by running:
+Release by running the following:
+   
+   $ git clean -fd && find . -name '*.pyc' -delete
+   $ python setup.py sdist --formats=gztar bdist_wheel
+   $ twine upload dist/*
    
-   $ python setup.py register sdist --formats=gztar bdist_wheel upload
-
-   to release a new version to PyPI.