Middleware object example using bound methods

The `ExampleComponent` interface example didn't work for me so I updated it to use bound methods on the piece of Middleware.

Is this how Middlware is used with Falcon?

```
from falcon import API

class Middleware(object):
    def process_request(self, req, resp, params):
        pass
    def process_response(self, req, resp):
        pass

app = API(middleware=Middleware())
```