Fix compatibility bug with django >= 1.4.2
Fix compatibility bug with django >= 1.4.2

hkmshb/django-select2-forms,sandow-digital/django-select2-forms,sandow-digital/django-select2-forms,SpectralAngel/django-select2-forms,JP-Ellis/django-select2-forms,hkmshb/django-select2-forms,hkmshb/django-select2-forms,sandow-digital/django-select2-forms,SpectralAngel/django-select2-forms,SpectralAngel/django-select2-forms