Separate logstash event creation from formatting operation - #51

    @Override
    public String format(LoggingEvent loggingEvent) {
       JSONObject logstashJson = createLogstashEvent(loggingEvent);
        String[] tags = new String[] {"CustomHardcodedTag"};
        logstashJson.put("tags", tags);

        return logstashJson.toString() + "\n";    
    }