Display ttyACM* devices in Serial Port list - Fixes #80526182

This change allows my printer (connected as /dev/ttyACM0) to appear in the list of ports and subsequently provides a way to select and connect to the machine. After making this change, dropping the baud rate to 115200 and installing Arduino, as well as having **it** prompt to modify some config settings to allow my user account to read/write to serial ports, I was able to connect and control my RAMP driven printer.

![prusai3](https://cloud.githubusercontent.com/assets/175113/4608509/ec19c11a-5281-11e4-9ffa-48558b01ba7b.png)