Added css target class to proerly display the 'move' cursor for sortable stacked inlines.
Refactored do_sorting_view to get start_index default value from len(indexes) rather than duplicate the line and set to 0.
Added NonSortableParentAdmin class to enable sorting URLs and JavaScript on models that do not inherit from Sortable.
Removed unused 'ordering' property on SortableAdmin.
Changed assignment of sorting_filters to use getattr, enabling NonSortableParentAdmin to inherit from SortableAdminBase.
Moved template properties to SortableAdminBase.
Added NonSortableCategory and SortableCategoryWidget model classes.
Wired up NonSortableCategory and inline sortable SortableCategoryWidget to sample project admin.
Added additional models for non sortable parent with sortable inlines.
Added new models and model admins to Python3 sample project.
Version bump to 1.7.4.
Updated readme with additional NonSortableParentAdmin related docs.
Updated readme docs for migrations.