add the casbin middleware to the list :heart:
@@ -23,6 +23,7 @@ Most of the experimental handlers are ported to work with _iris_'s handler form,
| [cloudwatch](https://github.com/iris-contrib/middleware/tree/master/cloudwatch) | AWS cloudwatch metrics middleware. |[iris-contrib/middleware/cloudwatch/_example](https://github.com/iris-contrib/middleware/tree/master/cloudwatch/_example) |
| [new relic](https://github.com/iris-contrib/middleware/tree/master/newrelic) | Official [New Relic Go Agent](https://github.com/newrelic/go-agent). | [iris-contrib/middleware/newrelic/_example](https://github.com/iris-contrib/middleware/tree/master/newrelic/_example) |
| [prometheus](https://github.com/iris-contrib/middleware/tree/master/prometheus)| Easily create metrics endpoint for the [prometheus](http://prometheus.io) instrumentation tool | [iris-contrib/middleware/prometheus/_example](https://github.com/iris-contrib/middleware/tree/master/prometheus/_example) |
+| [casbin](https://github.com/iris-contrib/middleware/tree/master/casbin)| An authorization library that supports access control models like ACL, RBAC, ABAC | [iris-contrib/middleware/casbin/_examples](https://github.com/iris-contrib/middleware/tree/master/casbin/_examples) |
Third-Party Handlers
------------
