Added Rollbar to premium sponsors

docs/index.md

@@ -75,10 +75,11 @@ The initial aim is to provide a single full-time position on REST framework.
     <li><a href="https://getsentry.com/welcome/" style="background-image: url(https://fund-rest-framework.s3.amazonaws.com/sentry130.png)">Sentry</a></li>
     <li><a href="https://getstream.io/try-the-api/?utm_source=drf&utm_medium=banner&utm_campaign=drf" style="background-image: url(https://fund-rest-framework.s3.amazonaws.com/stream-130.png)">Stream</a></li>
     <li><a href="https://hello.machinalis.co.uk/" style="background-image: url(https://fund-rest-framework.s3.amazonaws.com/Machinalis130.png)">Machinalis</a></li>
+    <li><a href="https://rollbar.com" style="background-image: url(https://fund-rest-framework.s3.amazonaws.com/rollbar.png)">Rollbar</a></li>
 </ul>
 <div style="clear: both; padding-bottom: 20px;"></div>
 
-*Many thanks to all our [wonderful sponsors][sponsors], and in particular to our premium backers, [Rover](http://jobs.rover.com/), [Sentry](https://getsentry.com/welcome/), [Stream](https://getstream.io/?utm_source=drf&utm_medium=banner&utm_campaign=drf), and [Machinalis](https://hello.machinalis.co.uk/).*
+*Many thanks to all our [wonderful sponsors][sponsors], and in particular to our premium backers, [Rover](http://jobs.rover.com/), [Sentry](https://getsentry.com/welcome/), [Stream](https://getstream.io/?utm_source=drf&utm_medium=banner&utm_campaign=drf), [Machinalis](https://hello.machinalis.co.uk/), and [Rollbar](https://rollbar.com).*
 
 ---