AttributeError: 'ForeignKeyField' object has no attribute 'to'
Thanks for fixing this one so quickly! When is the next release planned? Right now I'm using the master branch to get around this bug.

The create_foreign_key() function appears to be referencing an attribute that doesn't exist:

```
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "env/local/lib/python2.7/site-packages/peewee.py", line 2003, in create_table
    db.create_foreign_key(cls, field_obj)
  File "env/local/lib/python2.7/site-packages/peewee.py", line 1739, in create_foreign_key
    field.to._meta.db_table,
AttributeError: 'ForeignKeyField' object has no attribute 'to'
```

This occurs while running create_table() on a model that has a ForeignKeyField().

Running peewee version 2.0.2.
