21 improve scan serial output for linux

I tested on mac and I think it works better than before:
```
 ./gort scan serial                                      
/dev/cu.Bluetooth-Incoming-Port		/dev/cu.PebbleE36E-SerialPortSe		/dev/tty.Bluetooth-Incoming-Port	/dev/tty.PebbleE36E-SerialPortSe
/dev/cu.Bluetooth-Modem			/dev/cu.Sphero-YBW-RN-SPP		/dev/tty.Bluetooth-Modem		/dev/tty.Sphero-YBW-RN-SPP
```

So I vote for merge and create a new PR for upcoming changes..