Added legacy model definition back for seamless backwards compatibility.

Updated readme.
Added sample legacy model implementation.

sample_project/app/admin.py

@@ -7,7 +7,7 @@ from adminsortable.utils import get_is_sortable
 from app.models import (Category, Widget, Project, Credit, Note, GenericNote,
     Component, Person, NonSortableCategory, SortableCategoryWidget,
     SortableNonInlineCategory, NonSortableCredit, NonSortableNote,
-    CustomWidget, CustomWidgetComponent)
+    CustomWidget, CustomWidgetComponent, BackwardCompatibleWidget)
 
 
 admin.site.register(Category, SortableAdmin)
@@ -105,3 +105,4 @@ class CustomWidgetAdmin(SortableAdmin):
 
 admin.site.register(SortableNonInlineCategory, SortableAdmin)
 admin.site.register(CustomWidget, CustomWidgetAdmin)
+admin.site.register(BackwardCompatibleWidget, SortableAdmin)

sample_project/app/models.py

@@ -240,3 +240,14 @@ class CustomWidgetComponent(SortableMixin, SimpleModel):
 
     def __str__(self):
         return self.title
+
+
+@python_2_unicode_compatible
+class BackwardCompatibleWidget(Sortable, SimpleModel):
+
+    class Meta(Sortable.Meta):
+        verbose_name = 'Backward Compatible Widget'
+        verbose_name_plural = 'Backward Compatible Widgets'
+
+    def __str__(self):
+        return self.title