Missing documentation on website for the "magical" usage of ReplyException in EventBus?

I cannot seem to find documentation about the magical usage of ReplyException.class for the event bus. I came across it from looking at the ServiceProxy code.

This exception seems to be HUGELY important to sane usage of the event bus for what is considered a successful response from the event bus...

typically you would have to write:

```java
if (handler.succeeded(){
... write your additional inner checks of what is considered a success even though the EB returned a message
} else {
... handler.cause()
}
```

I have found that this pattern COMPLETELY changes the way you build on the EB and the way data is moved around.

Why is this seemingly not documented on the mains docs as a pattern to follow?