DOC: update CONTRIBUTING

Author: mgeier

CONTRIBUTING.rst

@@ -7,22 +7,25 @@ https://github.com/spatialaudio/python-pa-ringbuffer/.
 Contributions are always welcome!
 
 Instead of pip-installing the latest release from PyPI_, you should get the
-newest development version with Git::
+newest development version (a.k.a. "master") with Git::
 
    git clone https://github.com/spatialaudio/python-pa-ringbuffer.git
    cd python-pa-ringbuffer
-   python3 setup.py develop --user
+   python3 -m pip install -e . --user
 
-.. _PyPI: https://pypi.python.org/pypi/pa-ringbuffer
+... where ``-e`` stands for ``--editable``.
 
-This way, your installation always stays up-to-date, even if you pull new
-changes from the Github repository and if you switch between branches.
+When installing this way, you can quickly try other Git
+branches (in this example the branch is called "another-branch")::
 
-If you prefer, you can also replace the last command with::
+   git checkout another-branch
 
-   python3 -m pip install --user -e .
+If you want to go back to the "master" branch, use::
 
-... where ``-e`` stands for ``--editable``.
+   git checkout master
 
-In both cases you can drop the ``--user`` flag if you want a system-wide
-installation (assuming you have the necessary rights).
+To get the latest changes from Github, use::
+
+   git pull --ff-only
+
+.. _PyPI: https://pypi.python.org/pypi/pa-ringbuffer