Mod function or escape 
Unfortunately, peewee does not support modulo out of the box (because I ran out of operators to overload).

You can create your own operators, though...perhaps I should add this to the docs.  There are some cool examples in `playhouse.postgresql_ext` where I add operators for various hstore functions.  Here's how you do modulo and regexp:

``` python

from peewee import *
from peewee import Expr

def mod(lhs, rhs):
    return Expr(lhs, 'mod', rhs)

def regexp(lhs, rhs):
    return Expr(lhs, 're', rhs)

# tell sqlite what to do with these expressions
SqliteDatabase.register_ops({'mod': '%', 're': 'REGEXP'})

class User(Model):
    username = CharField()

# users whose username is all numbers
User.select().where(regexp(User.username, '[0-9]+')

# users with even ids
User.select().where(mod(User.id, 2) == 0)
```
 Docs: http://peewee.readthedocs.org/en/latest/peewee/querying.html#adding-user-defined-operators

I can't do a query where have to recover only even numbers.

Something like that:

Number.select().where(Number.number % 2 == 0)

This way, peewee 'translates' % for GLOB.

So, is there a way to escape % operator or a peewee.fn.Mod function?
