I was contemplating which style to pick but couldn't come up with a good reasoning. This makes sense, as they are macros.

For usage examples, see zmq.
https://github.com/kkoopa/zeromq.node/blob/v0.11/binding.cc#L750
https://github.com/JustinTulloss/zeromq.node/blob/master/binding.cc#L795

Regarding object access:
Would it work with a new macro:

```c++
//0.11
# define NAN_WKCB_OBJECT_REF(property) object->property
//0.10
# define NAN_WKCB_OBJECT_REF(property) object.property
```

Could do a similar thing for accessing the data argument, where the type has changed from void * to T *, and get rid of the useless init method. What should these macros be called?