Update arduino.ino

Instead of using a stepper controller, this allows for usage of some very cheap stepper motor/driver combos, specifically the UNL2003 stepper driver. 
Conceivably one could directly drive very low power steppers such as the ones harvested from cd drives.
This WILL be quite slow -- at best 1/4 of the adafruit, since your arduino now has to handle energizing individual coils.