Add easter egg

Signed-off-by: Syrone Wong <wong.syrone@gmail.com>

shadowsocks-csharp/View/MenuViewController.cs

@@ -566,7 +566,11 @@ namespace Shadowsocks.View
         {
             if (e.Button == MouseButtons.Left)
             {
-                // TODO: show something interesting
+                // Easter egg
+                _notifyIcon.BalloonTipTitle = "Keep a low profile";
+                _notifyIcon.BalloonTipText = "If you want to keep a secret, you must also hide it from yourself.";
+                _notifyIcon.BalloonTipIcon = ToolTipIcon.Warning;
+                _notifyIcon.ShowBalloonTip(5 * 1000);
             }
             else if (e.Button == MouseButtons.Middle)
             {