Add flushing render phase continuation 

```
Now that Issue 591 is fixed we can add a flushing render phase continuation 
that does: 
http://yehudakatz.com/2010/09/07/automatic-flushing-the-rails-3-1-plan/
```

Original issue reported on code.google.com by `philippe...@gmail.com` on 20 Jun 2012 at 5:11
