Clarify a few things in the README

Author: nedbat

README.rst

@@ -24,9 +24,15 @@ You will see your templates listed in your coverage report alongside your
 Python modules.
 
 If you get a django.core.exceptions.ImproperlyConfigured error, you need to set
-the DJANGO_SETTINGS_MODULE environment variable.  You may also have problems
-with importing the settings module with coverage commands.  You can set
-PYTHONPATH=. to fix that. I'm interested in ideas about how to fix this better.
+the DJANGO_SETTINGS_MODULE environment variable.
+
+
+Configuration
+-------------
+
+The Django template plugin uses some existing settings from your .coveragerc
+file.  The ``source=``, ``include=``, and ``omit=`` options control what
+template files are included in the report.
 
 
 What the? How?