Improved formatting of deconstruct() docs.

You can let Django serialize your own custom class instances by giving the class

a ``deconstruct()`` method. It takes no arguments, and should return a tuple

of three things: ``(path, args, kwargs)``. Note this return value is different

from the ``deconstruct()`` method :ref:`for custom fields

<custom-field-deconstruct-method>` which returns a tuple of four items.

of three things ``(path, args, kwargs)``:

``path`` should be the Python path to the class, with the class name included as the

last part (for example, ``myapp.custom_things.MyClass``). If your class is not

available at the top level of a module it is not serializable.

* ``path`` should be the Python path to the class, with the class name included

  as the last part (for example, ``myapp.custom_things.MyClass``). If your

  class is not available at the top level of a module it is not serializable.

``args`` should be a list of positional arguments to pass to your class'

* ``args`` should be a list of positional arguments to pass to your class'

  ``__init__`` method. Everything in this list should itself be serializable.

``kwargs`` should be a dict of keyword arguments to pass to your class'

* ``kwargs`` should be a dict of keyword arguments to pass to your class'

  ``__init__`` method. Every value should itself be serializable.

.. note::

    This return value is different from the ``deconstruct()`` method

    :ref:`for custom fields <custom-field-deconstruct-method>` which returns a

    tuple of four items.

Django will write out the value as an instantiation of your class with the

given arguments, similar to the way it writes out references to Django fields.