Unable to compare followed reverse foreign relation fields that are on a non-abstract parent class

[LegoStormtroopr]

For example, given the models and register below:

class Association(Model):
    related_to = ForeignKey('Parent',related_name='associations')

class Parent(Model):
    text = TextField(null=True)

class Child(Parent):
    more_text = TextField(null=True)

reversion.revisions.register(Child, follow=['parent_ptr','associations'])

Both the parent and child instances will be stored in the relation, but due to how django serialisers work for multi-table inheritance the associations field will only be available on the Parent reversion, not the Child reversion. I've made a PR that addresses that will be added soon.

[jedie]

PR always welcome! Please add a test, too ;)