Make AsyncTestCase call tearDown in super class.

The setUp method was calling super, but tearDown wasn't.  Now they
both are.

This change includes a new unit test case to verify the fix.

tornado/test/testing_test.py

@@ -11,5 +11,33 @@ def test_exception_in_callback(self):
         except ZeroDivisionError:
             pass
 
+class SetUpTearDownTest(unittest.TestCase):
+    def test_set_up_tear_down(self):
+        """
+        This test makes sure that AsyncTestCase calls super methods for
+        setUp and tearDown.
+
+        InheritBoth is a subclass of both AsyncTestCase and
+        SetUpTearDown, with the ordering so that the super of
+        AsyncTestCase will be SetUpTearDown.
+        """
+        events = []
+        result = unittest.TestResult()
+
+        class SetUpTearDown(unittest.TestCase):
+            def setUp(self):
+                events.append('setUp')
+
+            def tearDown(self):
+                events.append('tearDown')
+
+        class InheritBoth(AsyncTestCase, SetUpTearDown):
+            def test(self):
+                events.append('test')
+
+        InheritBoth('test').run(result)
+        expected = ['setUp', 'test', 'tearDown']
+        self.assertEqual(expected, events)
+
 if __name__ == '__main__':
-    unittest.main
+    unittest.main()

tornado/testing.py

@@ -112,6 +112,7 @@ def tearDown(self):
                     logging.debug("error closing fd %d", fd, exc_info=True)
             self.io_loop._waker_reader.close()
             self.io_loop._waker_writer.close()
+        super(AsyncTestCase, self).tearDown()
 
     def get_new_ioloop(self):
         '''Creates a new IOLoop for this test.  May be overridden in