FlaskDB and Model with signal support
Just subclass `FlaskDB` and override the `get_model` method to use the `Model` subclass from the `signals` extension:

``` python
from playhouse.signals import Model as SignalModel


class SignalsFlaskDB(FlaskDB):
    def get_model_class(self):
        if self.database is None:
            raise RuntimeError('Database must be initialized.')

        class BaseModel(SignalModel):
            class Meta:
                database = self.database

        return BaseModel
```

Voila!

Now `BaseModel` [class based on](https://github.com/coleifer/peewee/blob/master/playhouse/flask_utils.py#L153) peewee.Model without signals
