Unhandled error `Cannot read property 'statusCode'`

```
TypeError: Cannot read property 'statusCode' of undefined
   at Request._callback (....../node_modules/keycdn/index.js:43
```
Maybe response can be undefined in the `request` callback? :confused: 
https://github.com/keycdn/node-keycdn-api/blob/master/index.js#L43

It happened on zone creation.
`"keycdn": "^0.2.2"`

