Document peewee 3 change of `register_fields`.

I’m just getting around to updating my project to use peewee 3. I got most of what is in the differences page, but it doesn’t mention register_fields class method of PostgresExtDatabase is also now missing. How should I handle that?

[coleifer]

You don’t need to register anything anymore.

class MyMagicalField(Field):
    field_type = 'column_data_type'

    def special_field_expression(self, value):
        return Expression(self, 'operator', value)

[coleifer]

I’ve pushed a new release, 3.0.11, if you’re interested.