Swagger now uses 'message' rather than 'reason' for API error/status codes

I've noticed that using the latest swagger UI (http://petstore.swagger.wordnik.com/) my HTTP status codes no longer show the explanation text. Taking a quick look through the json, it seems that the petstore example uses the following json object:
```
{
    "code": 400,
    "message": "Invalid username supplied"
}
```

At the moment, swagger-springmvc generates:
```
{
    "code": 400,
    "reason": "Invalid username supplied"
}
```

This should fix that behaviour.