Update comparison.md - Fix Broken Link (vuejs#2367)

Change http://riotjs.com/compare/#virtual-dom-vs-expressions-binding to https://v3.riotjs.now.sh/compare/#virtual-dom-vs-expressions-binding

Author: ikrydev

src/v2/guide/comparison.md

@@ -224,5 +224,5 @@ In Polymer, the team has also made its data-binding system very limited in order
 
 Riot 3.0 provides a similar component-based development model (which is called a "tag" in Riot), with a minimal and beautifully designed API. Riot and Vue probably share a lot in design philosophies. However, despite being a bit heavier than Riot, Vue does offer some significant advantages:
 
-- Better performance. Riot [traverses a DOM tree](http://riotjs.com/compare/#virtual-dom-vs-expressions-binding) rather than using a virtual DOM, so suffers from the same performance issues as AngularJS.
+- Better performance. Riot [traverses a DOM tree](https://v3.riotjs.now.sh/compare/#virtual-dom-vs-expressions-binding) rather than using a virtual DOM, so suffers from the same performance issues as AngularJS.
 - More mature tooling support. Vue provides official support for [webpack](https://github.com/vuejs/vue-loader) and [Browserify](https://github.com/vuejs/vueify), while Riot relies on community support for build system integration.