mypy and mypy_extensions aren't posix only (#3765)

setup.py

diff --git a/setup.py b/setup.py
index 417b3fd..4a0b8ae 100644
--- a/setup.py
+++ b/setup.py
@@ -17,7 +17,6 @@
     'Environment :: Console',
     'Intended Audience :: Developers',
     'License :: OSI Approved :: MIT License',
-    'Operating System :: POSIX',
     'Programming Language :: Python :: 2',
     'Programming Language :: Python :: 2.7',
     'Programming Language :: Python :: 3',
@@ -37,7 +36,6 @@
     author_email='jukka.lehtosalo@iki.fi',
     url='http://www.mypy-lang.org/',
     license='MIT License',
-    platforms=['POSIX'],
     py_modules=['mypy_extensions'],
     classifiers=classifiers,
     install_requires=[