Fix that XVim sometimes fail to hook Xcode classes.
The reason was that NSApplicationDidFinishLaunching notificaion is not delivered correctly
(I do not know why but we often can not get the notificaion. This happens when Xcode open with "project selection window"
 Thid does not happen when Xcode directly open a workspace window.)
Anyway as far as I tested I do not need to wait the notification to hook classes.
The reason why we used the notification was related to issue #12
Currently it looks that IDESourceCodeEditor are loaded before our plugin.