Small improvement to the `contrib.messages` doc introduction.

.. module:: django.contrib.messages

   :synopsis: Provides cookie- and session-based temporary message storage.

Django provides full support for cookie- and session-based messaging, for

both anonymous and authenticated clients. The messages framework allows you

to temporarily store messages in one request and retrieve them for display

in a subsequent request (usually the next one). Every message is tagged

with a specific ``level`` that determines its priority (e.g., ``info``,

``warning``, or ``error``).

Quite commonly in web applications, you may need to display a one-time

notification message (also know as "flash message") to the user after

processing a form or some other types of user input. For this, Django provides

full support for cookie- and session-based messaging, for both anonymous and

authenticated users. The messages framework allows you to temporarily store

messages in one request and retrieve them for display in a subsequent request

(usually the next one). Every message is tagged with a specific ``level`` that

determines its priority (e.g., ``info``, ``warning``, or ``error``).

Enabling messages

=================