Fix template syntax error when using django 1.5

In django 1.5 the `{% url %}` tag no longer accepts a view name unless it's quoted correctly. This fixes the broken tag in django-tinymce and the two mentions in the docs.

While the `{% load url from future %}` is unnecessary in 1.5, it's required for backwards compatibility with django 1.4.

https://docs.djangoproject.com/en/1.5/internals/deprecation/#id2