tkinter._flatten and others not (easily) accessible #233

Hello,

The tkinter package included here does a from Tkinter import *, which misses at least _flatten, and _cnfmerge which might be used by tk extensions. Therefore the typical method of handling Python 2/3 causes it to stop working when combined with python-future. Example:

try:
     import tkinter
except ImportError:
     import Tkinter as tkinter

after running the above on stock Python 2 or Python 3 tkinter._flatten is available, but not when using python-future. Packages that make use of that need to be patched with something like:

if not hasattr(tkinter, '_flatten'):
     from Tkinter import _flatten, _cnfmerge
     tkinter._flatten = _flatten
     tkinter._cnfmerge = _cnfmerge