routing.md change link to vue-router docs

Author: Alex-Sokolov

src/v2/guide/routing.md

@@ -6,7 +6,7 @@ order: 21
 
 ## Official Router
 
-For most Single Page Applications, it's recommended to use the officially-supported [vue-router library](https://github.com/vuejs/vue-router). For more details, see vue-router's [documentation](http://vuejs.github.io/vue-router/).
+For most Single Page Applications, it's recommended to use the officially-supported [vue-router library](https://github.com/vuejs/vue-router). For more details, see vue-router's [documentation](http://router.vuejs.org/).
 
 ## Simple Routing From Scratch