Problems using order_by
I replaced the line 786 by 

```
parts.append('ORDER BY %s' % tuple(_)) 
```
 I can understnad your confusion.  Peewee uses "-<field name>" to specify ordering in a models "Meta" attributes.

However, when querying you will use a different syntax:

``` python

M.select().order_by(M.number.desc())
```

This is covered in the docs: 
- http://peewee.readthedocs.org/en/latest/peewee/cookbook.html#sorting-records
- http://peewee.readthedocs.org/en/latest/peewee/api.html#SelectQuery.order_by
 Thanks, man. Sorry about the false issue.

When running the script below, I got  

sqlite3.ProgrammingError: Incorrect number of bindings supplied. The current statement uses 1, and there are 0 supplied.

It seems that orm is not filling the resultant sql with fields to order.

When debugging, printing Ms of line 27 outputs :

<class '__main__.M'> SELECT t1."id", t1."number" FROM "m" AS t1 ORDER BY ? []
###### ######## Script to reproduce error

```
from peewee import IntegerField, Model, SqliteDatabase
import os
DBNAME = 'test.db'
db = SqliteDatabase(DBNAME)

class M(Model):
    number = IntegerField()
    class Meta:
        database = db

def init():
    # create table
    if not os.path.exists(DBNAME):
        M.create_table()

    #populate

    m1 = M()
    m1.number = 1
    m1.save()

    m2 = M()
    m2.number = 2
    m2.save()

def query():
    Ms = M.select().order_by('-number',)
    for m in Ms:
        print m

if __name__ == '__main__':
    init()
    query() 
```
