Initial pass of removing Python 2 support

This commit removes Six as a dependency for Pelican, replacing the
relevant aliases with the proper Python 3 imports. It also removes
references to Python 2 logic that did not require Six.

setup.py

@@ -1,5 +1,5 @@
 #!/usr/bin/env python
-import sys
+
 from io import open
 from os import walk
 from os.path import join, relpath
@@ -10,8 +10,7 @@ from setuptools import setup
 version = "4.2.0"
 
 requires = ['feedgenerator >= 1.9', 'jinja2 >= 2.7', 'pygments', 'docutils',
-            'pytz >= 0a', 'blinker', 'unidecode', 'six >= 1.4',
-            'python-dateutil']
+            'pytz >= 0a', 'blinker', 'unidecode', 'python-dateutil']
 
 entry_points = {
     'console_scripts': [
@@ -25,9 +24,7 @@ entry_points = {
 README = open('README.rst', encoding='utf-8').read()
 CHANGELOG = open('docs/changelog.rst', encoding='utf-8').read()
 
-description = u'\n'.join([README, CHANGELOG])
-if sys.version_info.major < 3:
-    description = description.encode('utf-8')
+description = '\n'.join([README, CHANGELOG])
 
 setup(
     name='pelican',