Find_port as module

[vascotenner]

With this additions, find port can be imported as module. Furthermore I removed unused imports and code.

[dhylands]

I tried to run this on my dev machine and got this error:

581 >./find_port.py
Traceback (most recent call last):
  File "./find_port.py", line 143, in <module>
    main()
  File "./find_port.py", line 136, in main
    if is_usb_serial(device, **args):
TypeError: is_usb_serial() argument after ** must be a mapping, not Namespace

I tried using both python2 and python3

[vascotenner]

I have fixed this bug and tested it in both python2 and 3.