Fix history forms for primary keys besides "id"
Fix history forms for primary keys besides "id"

pombredanne/django-simple-history,luzfcb/django-simple-history,luzfcb/django-simple-history,treyhunner/django-simple-history,emergence/django-simple-history,emergence/django-simple-history,treyhunner/django-simple-history,pombredanne/django-simple-history