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>

test/test_abstract_base_class.py

@@ -7,10 +7,6 @@
 :license: MIT
 """
 
-from __future__ import absolute_import
-from __future__ import division
-from __future__ import print_function
-from __future__ import unicode_literals
 
 from nose.tools import raises
 

test/test_cli.py

@@ -2,10 +2,6 @@
 
 """
 
-from __future__ import absolute_import
-from __future__ import division
-from __future__ import print_function
-from __future__ import unicode_literals
 
 import os
 import sys

test/test_function_barcode.py

@@ -1,8 +1,4 @@
 #!/usr/bin/python
-from __future__ import absolute_import
-from __future__ import division
-from __future__ import print_function
-from __future__ import unicode_literals
 
 import escpos.printer as printer
 from escpos.constants import BARCODE_TYPE_A, BARCODE_TYPE_B

test/test_function_cashdraw.py

@@ -1,8 +1,4 @@
 #!/usr/bin/python
-from __future__ import absolute_import
-from __future__ import division
-from __future__ import print_function
-from __future__ import unicode_literals
 
 import escpos.printer as printer
 from escpos.exceptions import CashDrawerError

test/test_function_check_barcode.py

@@ -1,10 +1,6 @@
 #!/usr/bin/python
 # -*- coding: utf-8 -*-
 
-from __future__ import absolute_import
-from __future__ import division
-from __future__ import print_function
-from __future__ import unicode_literals
 
 import escpos.printer as printer
 import pytest

test/test_function_cut.py

@@ -1,7 +1,3 @@
-from __future__ import absolute_import
-from __future__ import division
-from __future__ import print_function
-from __future__ import unicode_literals
 
 import six
 

test/test_function_image.py

@@ -7,10 +7,6 @@
 :license: MIT
 """
 
-from __future__ import absolute_import
-from __future__ import division
-from __future__ import print_function
-from __future__ import unicode_literals
 
 import pytest
 

test/test_function_linedisplay.py

@@ -7,10 +7,6 @@
 :license: MIT
 """
 
-from __future__ import absolute_import
-from __future__ import division
-from __future__ import print_function
-from __future__ import unicode_literals
 
 import escpos.printer as printer
 

test/test_function_panel_button.py

@@ -7,10 +7,6 @@
 :license: MIT
 """
 
-from __future__ import absolute_import
-from __future__ import division
-from __future__ import print_function
-from __future__ import unicode_literals
 
 import escpos.printer as printer
 

test/test_function_qr_native.py

@@ -7,10 +7,6 @@
 :license: MIT
 """
 
-from __future__ import absolute_import
-from __future__ import division
-from __future__ import print_function
-from __future__ import unicode_literals
 
 from nose.tools import raises
 import pytest

test/test_function_qr_non-native.py

@@ -8,10 +8,6 @@
 :license: MIT
 """
 
-from __future__ import absolute_import
-from __future__ import division
-from __future__ import print_function
-from __future__ import unicode_literals
 
 import pytest
 import mock

test/test_function_set.py

@@ -1,7 +1,3 @@
-from __future__ import absolute_import
-from __future__ import division
-from __future__ import print_function
-from __future__ import unicode_literals
 
 import six
 

test/test_function_softbarcode.py

@@ -1,8 +1,4 @@
 #!/usr/bin/python
-from __future__ import absolute_import
-from __future__ import division
-from __future__ import print_function
-from __future__ import unicode_literals
 
 import escpos.printer as printer
 import pytest

test/test_function_text.py

@@ -7,10 +7,6 @@
 :license: MIT
 """
 
-from __future__ import absolute_import
-from __future__ import division
-from __future__ import print_function
-from __future__ import unicode_literals
 
 import pytest
 import mock

test/test_load_module.py

@@ -7,10 +7,6 @@
 :license: MIT
 """
 
-from __future__ import absolute_import
-from __future__ import division
-from __future__ import print_function
-from __future__ import unicode_literals
 
 import escpos.printer as printer
 

test/test_magicencode.py

@@ -8,10 +8,6 @@
 :license: MIT
 """
 
-from __future__ import absolute_import
-from __future__ import division
-from __future__ import print_function
-from __future__ import unicode_literals
 
 import pytest
 from nose.tools import raises, assert_raises

test/test_printer_file.py

@@ -8,10 +8,6 @@
 :license: MIT
 """
 
-from __future__ import absolute_import
-from __future__ import division
-from __future__ import print_function
-from __future__ import unicode_literals
 
 import six
 

test/test_raise_arbitrary_error.py

@@ -7,10 +7,6 @@
 :license: MIT
 """
 
-from __future__ import absolute_import
-from __future__ import division
-from __future__ import print_function
-from __future__ import unicode_literals
 
 import pytest
 import escpos

test/test_with_statement.py

@@ -7,10 +7,6 @@
 :license: MIT
 """
 
-from __future__ import absolute_import
-from __future__ import division
-from __future__ import print_function
-from __future__ import unicode_literals
 
 import escpos.printer as printer
 import escpos.escpos as escpos