PySerial DC Motor Demo

This is code for a PySerial DC Motor Control Demo. The stepper motor code will be written added tomorrow, once Ry's got the stepper-handling circuit built (and I'm there to work on it with him). 
You know, I'm not entirely sure. It's in the Adafruit demo code, so I moved it over just to be safe. My best guess is that something funky happens the first time you send a command to the motor. Might be able to find something in the documentation later today, but I'd hardly call it a priority (seeing as in the final code we'll have to zero on startup anyways).