Die immediately on SIGINT if not in a tty

Closes gh-146

notebook/notebookapp.py

@@ -894,7 +894,7 @@ class NotebookApp(JupyterApp):
             log("Terminals not available (error was %s)", e)
 
     def init_signal(self):
-        if not sys.platform.startswith('win'):
+        if not sys.platform.startswith('win') and sys.stdin.isatty():
             signal.signal(signal.SIGINT, self._handle_sigint)
         signal.signal(signal.SIGTERM, self._signal_stop)
         if hasattr(signal, 'SIGUSR1'):