Changes from @takluyver @minrk review

Author: willingc

setup.py

@@ -79,16 +79,10 @@ def run(self):
         'Intended Audience :: System Administrators',
         'Intended Audience :: Science/Research',
         'License :: OSI Approved :: BSD License',
-        'Operating System :: MacOS',
-        'Operating System :: Microsoft :: Windows',
-        'Operating System :: POSIX :: Linux',
+        'Operating System :: Independent',
         'Programming Language :: Python',
-        'Programming Language :: Python :: 2.7',
+        'Programming Language :: Python :: 2',
         'Programming Language :: Python :: 3',
-        'Programming Language :: Python :: 3.3',
-        'Programming Language :: Python :: 3.4',
-        'Programming Language :: Python :: 3.5',
-        'Programming Language :: Python :: 3.6',
     ],
     install_requires = [
         'traitlets',
@@ -98,7 +92,7 @@ def run(self):
         'entrypoints',
         'tornado>=4.1',
     ],
-    python_requires='>=2.7, !=3.0.*, !=3.1.*, !=3.2.*, <4',
+    python_requires='>=2.7, !=3.0.*, !=3.1.*, !=3.2.*, >=3.3',
     extras_require   = {
         'test': ['ipykernel', 'ipython', 'mock'],
         'test:python_version == "3.3"': ['pytest<3.3.0'],