Merge pull request #18 from wharton/abstractitemmodel

Changed model GridItem to be an abstract model, GridItemAbstract.

wagtailgridder/models.py

@@ -42,17 +42,14 @@ class Meta:
         verbose_name_plural = "grid categories"
 
 
-class GridItem(Page):
+class GridItemAbstract(models.Model):
     """
     The fields needed to properly display a grid item.
     The template will omit any fields not included automagically.
     """
 
     parent_page_types = get_grid_item_parent_page_types()
 
-    class Meta:
-        verbose_name = "Grid Item"
-
     summary_image = models.ForeignKey(
         "wagtailimages.Image",
         null=True,
@@ -139,11 +136,23 @@ class Meta:
         ),
     ]
 
+    class Meta:
+        abstract = True
+
     def save(self, *args, **kwargs):
         self.modified = timezone.now()
         super().save(*args, **kwargs)
 
 
+class GridItem(GridItemAbstract, Page):
+    """
+    Concrete implementation of GridItemAbstract.
+    """
+
+    class Meta:
+        verbose_name = "Grid Item"
+
+
 class GridIndexGridItemRelationship(Orderable, models.Model):
     """
     Allows the content creator to associate Grid Items on a