Added a note that cleaned_data is new in the development release.

    >>> f.cleaned_data

    {'cc_myself': True, 'message': u'Hi there', 'sender': u'foo@example.com', 'subject': u'hello'}

.. note::

    **New in Django development version** The ``cleaned_data`` attribute was

    called ``clean_data`` in earlier releases.

Note that any text-based field -- such as ``CharField`` or ``EmailField`` --

always cleans the input into a Unicode string. We'll cover the encoding

implications later in this document.