document in terms of -m fissix

Author: graingert

README.rst

@@ -10,8 +10,9 @@ This library is a very thin wrapper around `fissix
 to make Python 2 code more modern with the intention of eventually
 porting it over to Python 3.
 
-The ``python -m modernize`` command works like `fissix
-<https://github.com/jreese/fissix>`_. Here's how you'd rewrite a
+The ``python -m modernize`` command works like
+``python -m fissix``, see `fissix <https://github.com/jreese/fissix>`_.
+Here's how you'd rewrite a
 single file::
 
     python -m modernize -w example.py