OS X: Prevent white flash on window open

We got the window to run less JS but now it’s shown by the main process
too soon! This fixes that with a setTimeout.

Perhaps when this issue is fixed
(https://github.com/atom/electron/issues/861) we can remove the timeout.

main/windows.js

@@ -71,10 +71,6 @@ function createMainWindow () {
     menu.onToggleFullScreen()
   })
 
-  win.webContents.on('did-finish-load', function () {
-    win.show()
-  })
-
   win.on('blur', menu.onWindowHide)
   win.on('focus', menu.onWindowShow)