middleware for CMS logging out all sneakpeek users

Handles sneakpeek users showing up on CMS.

@sefk @jrbl
Are there ever times that request.user is not defined?   I know that's not typical, but since this runs for *any* request, seems like some defensive programming here might provide some safety.  LIke this:

```
if request.user and request.user.is_anonymous():
```