Fixed Tornado worker exiting.

Thanks to Masahiro Nakagawa for the report and patch.

Fixes #216

THANKS

@@ -29,3 +29,4 @@ Dan Sully <daniel-github@electricrain.com>
 Fabian Topfstedt <topfstedt@schneevonmorgen.com>
 Denis Bilenko <denis.bilenko@gmail.com>
 Michael Schurter <m@schmichael.com>
+Masahiro Nakagawa <repeatedly@gmail.com>

gunicorn/workers/gtornado.py

@@ -30,6 +30,10 @@ class TornadoWorker(Worker):
         web.RequestHandler.clear = clear
         sys.modules["tornado.web"] = web
         
+    def handle_quit(self, sig, frame):
+        super(TornadoWorker, self).handle_quit(sig, frame)
+        self.ioloop.stop()
+
     def watchdog(self):
         self.notify()