can't unload/destroy fragments?

Not sure if this is a bug or desired feature, but If I do the following:

```
fragment = this.get('store').createFragment('thingy')
fragment.unloadRecord()
```

I get the error:

```
EmberError {description: undefined, fileName: undefined, lineNumber: undefined, message: "Attempted to handle event `unloadRecord` on while in state root.loaded.created. ", name: "Error"…}
```

Should the record be just removed?