Support the more flattened HTTP response, supporting nsq v1+

[abourget]

I noticed in handler.go:

	v1 := req.Header.Get("Accept") == "application/vnd.nsq; version=1.0"

	if !v1 {
		value = struct {
			StatusCode int         `json:"status_code"`
			StatusText string      `json:"status_txt"`
			Data       interface{} `json:"data"`
		}{
			StatusCode: status,
			StatusText: text,
			Data:       value,
		}
	}

We could also do something similar here to support both versions.. a bit more refactoring would need to happen through, to bubble up the headers alongside the ret, or the ret could be a channel of more structured objects, like the LookupResult itself..