待增补内容

这里主要放日常看到，但暂时写不进去的内容。

Vue 2.4

其更新日志中写到：

• Full SSR + async component support in core: SSR now supports rendering async components used anywhere and the client also supports async components during the hydration phase. This means async components / code-splitting now just works during SSR and is no longer limited at the route level.

看看是不是合适加进去。