Spark

Spark.io support
If the Spark is just another "arduino" then it may make sense to included it with the firmata/arduino stuff. By this I mean if you can already use most Arduino libraries with the Spark, you program it with the Arduino IDE, etc. If that is not the case it may be better to create a separate repo firmata/spark. The reason being that I wouldn't want to maintain exceptions for boards that are only partially Arduino compatible.