Cleaned up some small formatting in docs/authentication.txt

``user_permissions``. ``User`` objects can access their related

objects in the same way as any other `Django model`_::

    ``myuser.objects.groups = [group_list]``

    ``myuser.objects.groups.add(group, group,...)``

    ``myuser.objects.groups.remove(group, group,...)``

    ``myuser.objects.groups.clear()``

    ``myuser.objects.permissions = [permission_list]``

    ``myuser.objects.permissions.add(permission, permission, ...)``

    ``myuser.objects.permissions.remove(permission, permission, ...]``

    ``myuser.objects.permissions.clear()``

    myuser.objects.groups = [group_list]

    myuser.objects.groups.add(group, group,...)

    myuser.objects.groups.remove(group, group,...)

    myuser.objects.groups.clear()

    myuser.objects.permissions = [permission_list]

    myuser.objects.permissions.add(permission, permission, ...)

    myuser.objects.permissions.remove(permission, permission, ...]

    myuser.objects.permissions.clear()

In addition to those automatic API methods, ``User`` objects have the following

custom methods: