Finalize python2/3 codebase compatibility and get rid of 2to3

setup.py

@@ -118,8 +118,8 @@ extra_opts = {
         "Pillow>=2.0.0",
     ],
 }
+
 if sys.version_info[0] == 3:
-    extra_opts["use_2to3"] = True
     if "test" in sys.argv:
         extra_opts["packages"] = find_packages()
         extra_opts["package_data"] = {
@@ -143,7 +143,7 @@ setup(
     long_description=LONG_DESCRIPTION,
     platforms=["any"],
     classifiers=CLASSIFIERS,
-    install_requires=["pymongo>=3.4", "six>=1.10.0"],
+    install_requires=['pymongo>=3.4', 'six', 'future'],
     cmdclass={"test": PyTest},
     **extra_opts
 )