Support for stepper control using stepperFirmata developed by Maxuino

I submitted a pull request to firmata.js to add support the stepper protocol developed by Maxuino (see: http://www.maxuino.org/downloads)  
https://github.com/jgautier/firmata/pull/24

This pull request adds the wrappers to the functionality in johnny-five

Let me know if I need to change anything for this