How to select on basis of ForeignKeyField.attribute == 'something'
You're close, but you will need to perform a join.  Check out the docs on joining: http://peewee.readthedocs.org/en/latest/peewee/querying.html#joining-tables

``` python
result = Secondary.select().join(Primary).where(Primary.prim_attr == 'something')
```

I have two models:

```
class Primary(db.Model):
    prim_attr = CharField()

class Secondary(db.Model):
    primary = ForeignKeyField(Primary, related_name='secondaries')
    sec_attr = IntegerField()
```

I want to get all secondary items where the primary.prim_attr equals 'something'. So I tried to do like this:

```
result = Secondary.select().where(Secondary.primary.prim_attr == 'something')
```

But I get an error: AttributeError: 'ForeignKeyField' object has no attribute 'prim_attr'.

I can get the Primary object first, and then insert in the second query like this:

```
result = Secondary.select().where(Secondary.primary == primaryObject)
```

But it is easier if I can do it in one line. Is that possible?
