Rename should throw an error for invalid property . 

Error should be throw when rename is invoked on a property which does not exist in the object. 
This will avoid making a valid property undefined. 
e.g
```javascript
var obj = {a: 1, b:2};
Hoek.rename(obj, 'd', 'a');  // --> Should throw an error that 'd' is not a valid property.
console.log(obj); 
// result {a:undefined, b:2}
```