don't spam the console

SIGWINCH could happen often in the console when the terminal is resized.
Since the error is harmless just display it when the logging level is
debug.

fix #449

gunicorn/arbiter.py

@@ -281,7 +281,7 @@ class Arbiter(object):
             self.num_workers = 0
             self.kill_workers(signal.SIGQUIT)
         else:
-            self.log.info("SIGWINCH ignored. Not daemonized")
+            self.log.debug("SIGWINCH ignored. Not daemonized")
 
     def wakeup(self):
         """\