Removing unneeded from __future__ import statements.

Since we are on Python 3.6 and up, we don't need those anymore.

ebook_converter/ebooks/txt/txtml.py

@@ -1,20 +1,16 @@
-# -*- coding: utf-8 -*-
-from __future__ import absolute_import, division, print_function, unicode_literals
-
-__license__ = 'GPL 3'
-__copyright__ = '2009, John Schember <john@nachtimwald.com>'
-__docformat__ = 'restructuredtext en'
-
-'''
+"""
 Transform OEB content into plain text
-'''
-
+"""
 import re
 
 from lxml import etree
 from ebook_converter.polyglot.builtins import string_or_bytes
 
 
+__license__ = 'GPL 3'
+__copyright__ = '2009, John Schember <john@nachtimwald.com>'
+__docformat__ = 'restructuredtext en'
+
 BLOCK_TAGS = [
     'div',
     'p',