Merge pull request #322 from minrk/require-tornado

require tornado

Author: takluyver

setup.py

@@ -83,6 +83,7 @@ def run(self):
         'pyzmq>=13',
         'python-dateutil>=2.1',
         'entrypoints',
+        'tornado>=4.1',
     ],
     extras_require   = {
         'test': ['ipykernel', 'ipython', 'mock'],