add `icons` field to rocketbar search API endpoint (bug 1029635)

https://bugzilla.mozilla.org/show_bug.cgi?id=1029635

r? @robhudson

# v1
![](http://cl.ly/image/3z090m3K450Q/Screen%20Shot%202014-06-27%20at%207.01.03%20PM.png)

# v2
![](http://cl.ly/image/043D371d0g1N/Screen%20Shot%202014-06-27%20at%207.01.33%20PM.png)

What chuck wrote is valid. What's not valid is something like
```
response = self.client.get(url,
    data={'q': 'something', 'lang': 'en-US', 'limit': 1})
```