Moved test tag library to templatetags dir

Dynamic library registration is harder to do to keep backwards
compatibility.

+from django.template import Library
+
+register = Library()
+
+
+@register.filter
+def noop(variable, param=None):
+    return variable

 from __future__ import absolute_import
 
 from django.contrib.contenttypes.models import ContentType
-from django.template import Template, Context, Library
-from django.template.base import libraries
+from django.template import Template, Context
 
 from django_comments.forms import CommentForm
 from django_comments.models import Comment
@@ -10,15 +9,6 @@ from django_comments.models import Comment
 from testapp.models import Article, Author
 from . import CommentTestCase
 
-register = Library()
-
-
-@register.filter
-def noop(variable, param=None):
-    return variable
-
-libraries['comment_testtags'] = register
-
 
 class CommentTemplateTagTests(CommentTestCase):