History not logged when performing save on "proxy" model

[ndufrane]

Hi,

When using the admin app to make modification on a entity, the historical records are not created if the model is a proxy (https://docs.djangoproject.com/en/1.8/topics/db/models/#proxy-models) of a model with historical record activated.

With the example below, editing with the admin app the class Person works fine but not with MyPerson.

class Person(models.Model):
    first_name = models.CharField(max_length=30)
    last_name = models.CharField(max_length=30)
    history = HistoricalRecords()

class MyPerson(Person):
    class Meta:
        proxy = True

Do i miss something ?

[ndufrane]

Ok there is a PR for this #154