Change unicode to str in CreateView for Python 3

Hello. This fixes a NameError for me.
```
global name 'unicode' is not defined

/home/***/.virtualenvs/memoria/lib/python3.3/site-packages/autocomplete_light/views.py in respond_script
            unicode(obj.pk), unicode(obj).replace('"', '\\"'))) ...
```
I don't know if this is the best way, I think it only works for Python 3.