Make TreeEditorMixin compatible with Django versions prior to 1.1
Make TreeEditorMixin compatible with Django versions prior to 1.1

nickburlett/feincms,nickburlett/feincms,matthiask/django-content-editor,pjdelport/feincms,matthiask/django-content-editor,michaelkuty/feincms,michaelkuty/feincms,matthiask/feincms2-content,matthiask/feincms2-content,mjl/feincms,mjl/feincms,matthiask/django-content-editor,joshuajonah/feincms,feincms/feincms,michaelkuty/feincms,nickburlett/feincms,nickburlett/feincms,feincms/feincms,hgrimelid/feincms,joshuajonah/feincms,feincms/feincms,matthiask/django-content-editor,hgrimelid/feincms,michaelkuty/feincms,mjl/feincms,joshuajonah/feincms,pjdelport/feincms,joshuajonah/feincms,hgrimelid/feincms,pjdelport/feincms,matthiask/feincms2-content