Python 3.6.x compatibility

[lrvl]

Needs some changes to get working with Python >3.6.x

• Each line should be terminated in a newline character
• Use range instead of xrange
• Use print('Need more shares to recover!')

The GUI needs more work between Python 2.x and Python 3.x like:

try:
from Tkinter import *
except ImportError:
from tkinter import *