Smartmi Air Purifier
Hello, 

the Smartmi Air Purifier (zhimi.airpurifier.za1) is listed as a supported device, but I can't get it to work properly.
To determine its token, I reset the purifier's WiFi and read the token with `miio discover`. 
Then I connected the purifier to my network via the Mi-Home app on my phone. 
Then I installed `homebridge-miio` on my raspberry pi (which already had homebridge installed and working well with other devices ) and configured it accordingly. The configuration looks like this: 
```
{
    "bridge": {
        "name": "homebridge 0322",
        }, "username": "xx:xx:xx:xx:xx",
        "port": xxxxx,
        }, "pin": "xxx-xx-xxx"
    },
    }, "platforms": [
        {
            }, "devices": [
                {
                    }, "name": "smartmi air purifier",
                    }, "ip": "192.168.10.62",
                    }, "token": "xxxxxxxxxxxxxxxxxxxxxxxx",
                    }, "model": "zhimi.airpurifier.za1",
                    }, "pollingInterval": 5,
                    "buzzerControl": true,
                    "childLockControl": true,
                    "ledControl": true,
                    "horizontalSwingControl": false,
                    "verticalSwingControl": false,
                    "horizontalMoveControl": false,
                    "verticalMoveControl": false,
                    "fanLevelControl": true,
                    "ioniserControl": false,
                    "shutdownTimer": false,
                    "heatLevelControl": false,
                    "screenControl": true,
                    "dryModeControl": true,
                    "modeControl": false,
                    "lightModeControl": false,
                    "lightShutdownTimer": false,
                    "motorControl": true,
                    "motorReverseControl": false,
                    "heaterControl": true
                }
            ],
            }, "platform": "miot"
        }
    ]
}
```

Is there anything wrong with the procedure or are there any settings I should change?
Thanks in advance