drop Python 2.7 support

Python 2.7 EOL is arriving on 2020-01-01: https://pythonclock.org/

This will allow us to use Python 3 only libraries, like python-barcode,
which can maintain a reduced, simpler codebase, due to only one version
to support.

Closes #371.

Signed-off-by: Romain Porte <microjoe@microjoe.org>

src/escpos/__init__.py

@@ -2,10 +2,6 @@
 """
 python-escpos enables you to manipulate escpos-printers
 """
-from __future__ import absolute_import
-from __future__ import division
-from __future__ import print_function
-from __future__ import unicode_literals
 
 __all__ = ["constants", "escpos", "exceptions", "printer"]
 

src/escpos/cli.py

@@ -9,10 +9,6 @@ It requires you to have a configuration file. See documentation for details.
 
 """
 
-from __future__ import absolute_import
-from __future__ import division
-from __future__ import print_function
-from __future__ import unicode_literals
 
 import argparse
 try:

src/escpos/config.py

@@ -4,10 +4,6 @@ This module contains the implentations of abstract base class :py:class:`Config`
 
 """
 
-from __future__ import absolute_import
-from __future__ import division
-from __future__ import print_function
-from __future__ import unicode_literals
 
 import os
 import appdirs

src/escpos/constants.py

@@ -11,10 +11,6 @@ moved to `capabilities` as in `escpos-php by @mike42 <https://github.com/mike42/
 :license: MIT
 """
 
-from __future__ import absolute_import
-from __future__ import division
-from __future__ import print_function
-from __future__ import unicode_literals
 
 import six
 

src/escpos/escpos.py

@@ -10,10 +10,6 @@ This module contains the abstract base class :py:class:`Escpos`.
 :license: MIT
 """
 
-from __future__ import absolute_import
-from __future__ import division
-from __future__ import print_function
-from __future__ import unicode_literals
 
 import qrcode
 import textwrap

src/escpos/exceptions.py

@@ -25,11 +25,6 @@ Result/Exit codes:
 :license: MIT
 """
 
-from __future__ import absolute_import
-from __future__ import division
-from __future__ import print_function
-from __future__ import unicode_literals
-
 
 class Error(Exception):
     """ Base class for ESC/POS errors """

src/escpos/image.py

@@ -8,10 +8,6 @@ This module contains the image format handler :py:class:`EscposImage`.
 :license: MIT
 """
 
-from __future__ import absolute_import
-from __future__ import division
-from __future__ import print_function
-from __future__ import unicode_literals
 
 import math
 from PIL import Image, ImageOps

src/escpos/katakana.py

@@ -4,11 +4,6 @@
 I doubt that this currently works correctly.
 """
 
-from __future__ import absolute_import
-from __future__ import division
-from __future__ import print_function
-from __future__ import unicode_literals
-
 
 try:
     import jaconv

src/escpos/magicencode.py

@@ -12,10 +12,6 @@ The code is based on the encoding-code in py-xml-escpos by @fvdsn.
 :license: MIT
 """
 
-from __future__ import absolute_import
-from __future__ import division
-from __future__ import print_function
-from __future__ import unicode_literals
 
 from builtins import bytes
 from .constants import CODEPAGE_CHANGE

src/escpos/printer.py

@@ -8,7 +8,6 @@
 :license: MIT
 """
 
-from __future__ import absolute_import, division, print_function, unicode_literals
 
 import serial
 import socket