Remove load url from future

`{% load url from future %}` can be removed from templates since Django 1.5 and it will be removed from Django in 1.9

https://docs.djangoproject.com/en/1.8/releases/1.5/#django-1-5-release-notes
https://docs.djangoproject.com/en/dev/releases/1.7/#loading-ssi-and-url-template-tags-from-future-library

adminsortable/templates/adminsortable/change_form.html

@@ -1,6 +1,5 @@
 {% extends change_form_template_extends %}
 {% load i18n admin_modify %}
-{% load url from future %}
 {% load static from staticfiles %}
 
 {% block extrahead %}
@@ -30,4 +29,4 @@
 
 {% block after_related_objects %}{{ block.super }}
 <input type="hidden" id="localized_save_before_reorder_message" value="{% trans 'There are unsaved changes on this page. Please save your changes before reordering.' %}"/>
-{% endblock %}
+{% endblock %}