Adding another level of abstract modeling for Comment

This will ensure that custom comment apps don't trigger table joins or require `select_related()` to be used. Documentation updated.

@@ -43,7 +43,7 @@ class BaseCommentAbstractModel(models.Model):
 
 
 @python_2_unicode_compatible
-class Comment(BaseCommentAbstractModel):
+class CommentAbstractModel(BaseCommentAbstractModel):
     """
     A user comment about some object.
     """
@@ -76,7 +76,7 @@ class Comment(BaseCommentAbstractModel):
     objects = CommentManager()
 
     class Meta:
-        db_table = "django_comments"
+        abstract = True
         ordering = ('submit_date',)
         permissions = [("can_moderate", "Can moderate comments")]
         verbose_name = _('comment')
@@ -88,7 +88,7 @@ class Comment(BaseCommentAbstractModel):
     def save(self, *args, **kwargs):
         if self.submit_date is None:
             self.submit_date = timezone.now()
-        super(Comment, self).save(*args, **kwargs)
+        super(CommentAbstractModel, self).save(*args, **kwargs)
 
     def _get_userinfo(self):
         """
@@ -167,6 +167,11 @@ class Comment(BaseCommentAbstractModel):
         return _('Posted by %(user)s at %(date)s\n\n%(comment)s\n\nhttp://%(domain)s%(url)s') % d
 
 
+class Comment(CommentAbstractModel):
+    class Meta(CommentAbstractModel.Meta):
+        db_table = "django_comments"
+
+
 @python_2_unicode_compatible
 class CommentFlag(models.Model):
     """

@@ -61,21 +61,20 @@ the ``my_comment_app`` directory::
 In the ``models.py`` we'll define a ``CommentWithTitle`` model::
 
     from django.db import models
-    from django_comments.models import Comment
+    from django_comments.models import CommentAbstractModel
 
-    class CommentWithTitle(Comment):
+    class CommentWithTitle(CommentAbstractModel):
         title = models.CharField(max_length=300)
 
 Most custom comment models will subclass the
-:class:`~django_comments.models.Comment` model. However,
+:class:`~django_comments.models.CommentAbstractModel` model. However,
 if you want to substantially remove or change the fields available in the
-:class:`~django_comments.models.Comment` model, but don't want to
+:class:`~django_comments.models.CommentAbstractModel` model, but don't want to
 rewrite the templates, you could try subclassing from
 ``BaseCommentAbstractModel``.
 
 Next, we'll define a custom comment form in ``forms.py``. This is a little more
 tricky: we have to both create a form and override
-``CommentForm.get_comment_model()`` and
 ``CommentForm.get_comment_create_data()`` to return deal with our custom title
 field::