Remove root object, when `object @a => false`

View:
```ruby
object @object => false
attributes :id, :note
```
Before, it renders this:
```ruby
{
    "false": {
        "id": 1,
        "note": "bla bla bla"
    }
}
```
Wtf?

So, now it will render without root node:
```ruby
{
    "id": 1,
    "note": "bla bla bla"
}
```