Add more detail in docstring

codejail/django_integration.py

-"""Django integration for codejail"""
+"""Django integration for codejail.
+
+Code to glue codejail into a Django environment.
+
+"""
 
 from django.core.exceptions import MiddlewareNotUsed
 from django.conf import settings
@@ -7,8 +11,14 @@ import codejail.jail_code
 
 
 class ConfigureCodeJailMiddleware(object):
-    """Middleware to configure codejail on startup."""
+    """
+    Middleware to configure codejail on startup.
+
+    This is a Django idiom to have code run once on server startup: put the
+    code in the `__init__` of some middleware, and have it do the work, then
+    raise `MiddlewareNotUsed` to disable the middleware.
 
+    """
     def __init__(self):
         python_bin = settings.CODE_JAIL.get('python_bin')
         if python_bin: