simple functional way to create models
Thanks for your interest in peewee and for sharing your code.  I'm not sure this belongs as a github issue, as I use this to track bugs and new features, as opposed to snippets.

I actually working on tool for generate "dimension tables" for pentaho. I write this simple snippet for create models in more functional way.

``` python
#!/usr/bin/env python
# -*- coding: utf-8 -*-

from peewee import *

def create_model(model_name, supercls=(Model,), meta={}, **fields):
    """Create a model in functional way

    This 2 codes are equivalent

    >>> db = SqliteDatabase("foo.db")
    >>> class MyModel(Model):
    ...     name = TextField()
    ...     flag = BooleanField()
    ...        
    ...     class Meta:
    ...         database = db

    >>> db = SqliteDatabase("foo.db")
    >>> MyModel = create_model("MyModel",
    ...     meta={"database": db},
    ...     name=TextField(),
    ...     flag=Booleanfield()
    ...)


    """
    fields["Meta"] = type("Meta", (), meta)
    model = type(model_name, supercls, fields)
    return model
```

Maybe it will be useful for another developers to merge inside peewee (i replace sqlalchemy with this fragment of code) 
