bug 803607 - scrub email addresses in comments

I edited the file cached json and added an email address to:

```
    {
      "user_comments": "Refreshed page foo.bar@gmail.com",
      "date_processed": "2013-07-03T11:16:40+00:00",
      "email": null,
      "uuid": "30b6eb40-954a-46c0-b670-4bf502130703"
    },
```
Now it looks like this:
http://cl.ly/QAQ0