Duplicate results when iterating a select query and creating unrelated models
I found that wrapping the for loop in a transaction solves the problem, so I guess this is expected behavior.  It does still seem worth it to make this more clear in the documentation.
 Check out:
- https://github.com/coleifer/peewee/issues/12#issuecomment-5614404
- https://github.com/coleifer/peewee/issues/81

I know modification of an iterable while iterating over it can cause problems, but it seems surprising that I can't iterate a select query while creating completely unrelated model instances.

``` python
import peewee as pw

class DatabaseModel(pw.Model):
    class Meta:
        database = pw.SqliteDatabase(':memory:')

class A(DatabaseModel):
    name = pw.CharField()

class B(DatabaseModel):
    name = pw.CharField()

A.create_table()
B.create_table()

for name in ('test1', 'test2'):
    A.create(name=name)

for a in A.select():
    print a.name
    B.create(name='blah')
```

Produces:

```
test1
test2
test1
test2
```

Not sure if this is expected, but I couldn't find anything in the documentation.
