No PasswordField in playhouse.fields
Sorry for ignoring this tip
>Note
>This field requires bcrypt, which can be installed by running pip install bcrypt.
Hi

I got an error when trying to import PasswordField. Then I checked this
```python
>>> from playhouse import fields
>>> fields.P
fields.PY2                  fields.PickledField(        fields.PrimaryKeyField(     fields.Proxy(
fields.Param(               fields.PostgresqlDatabase(  fields.ProgrammingError(    
>>> import peewee
>>> peewee.__version__
peewee.__version__
>>> peewee.__version__
'2.8.5'
```

The only reason I supposed was that the os kernel was too old
```bash
$ uname -a
Linux prod-bj-sem-20-143 2.6.18-164.el5 #1 SMP Thu Sep 3 03:28:30 EDT 2009 x86_64 x86_64 x86_64 GNU/Linux
```
So should I install some extra libraries?