Unexpected behavior doing nested iteration on a SelectQuery
Here is a description of the problem:

``` python
# create 5 users, named user0-user4
query = User.select()
for o in query:
    print 'o ->', o.username
    for i in query:
        print '    i ->', i.username
```

This will print:

```
o -> u0
    i -> u0
    i -> u1
    i -> u2
    i -> u3
    i -> u4
```
 So when you iterate over a `SelectQuery` it creates a `QueryResultWrapper` which allows for efficient iteration and indexing. The problem is that the iterator is stateful.

The workaround I'd suggest is just to coerce to a `list` beforehand. You can also call `QueryResultWrapper.fill_cache()`.

I'll see about a better fix.
 This should now be fixed in master.
 Great, thanks!

Hi, I wanted to bring an issue to your attention: nested iteration of SelectQuery results doesn't work as expected. You can see an example, and a workaround, on my StackOverflow question:
http://stackoverflow.com/questions/31815235/python-peewee-iterate-over-selectquery

Is there an iterator that needs to be reset somewhere? Maybe at the end of the inner loop?

Thanks!
