register dynamic models too

[ChillarAnand]

right now, quickadmin registers only static models.

but if create a model on the fly like this

Person = type('Person', (models.Model,), {
    'first_name': models.CharField(max_length=255),
    'last_name': models.CharField(max_length=255),
 })

it wont appear.

it is neccessary to update the admin whenever a model is registered using class_prepared

@receiver(class_prepared)
def register_dynamic_models(sender, **kwargs):

[zniper]

Nice one, I haven't thought about this case.