Fix missing highlighting in some code examples

Given a ``Blog`` instance ``b5`` that has already been saved to the database,

this example changes its name and updates its record in the database::

    >> b5.name = 'New name'

    >> b5.save()

    >>> b5.name = 'New name'

    >>> b5.save()

This performs an ``UPDATE`` SQL statement behind the scenes. Django doesn't hit

the database until you explicitly call :meth:`~django.db.models.Model.save`.

Example::

    >> q1 = Entry.objects.filter(headline__startswith="What")

    >> q2 = q1.exclude(pub_date__gte=datetime.date.today())

    >> q3 = q1.filter(pub_date__gte=datetime.date.today())

    >>> q1 = Entry.objects.filter(headline__startswith="What")

    >>> q2 = q1.exclude(pub_date__gte=datetime.date.today())

    >>> q3 = q1.filter(pub_date__gte=datetime.date.today())

These three ``QuerySets`` are separate. The first is a base

:class:`~django.db.models.query.QuerySet` containing all entries that contain a

    >>> Entry.objects.filter(pub_date__lte='2006-01-01')

translates (roughly) into the following SQL::

translates (roughly) into the following SQL:

.. code-block:: sql

    SELECT * FROM blog_entry WHERE pub_date <= '2006-01-01';