Added link to CommonMark spec at visible place.

README.md

@@ -9,11 +9,9 @@
 
 __[Live demo](https://markdown-it.github.io)__
 
-__v4.+ changed internals! Plugins need update. See [migration details](https://github.com/markdown-it/markdown-it/blob/master/docs/4.0_migration.md)__
-
-- Supports the CommonMark spec + syntax extensions + sugar (URL autolinking, typographer).
+- Follows the __[CommonMark spec](http://spec.commonmark.org/)__ + adds syntax extensions & sugar (URL autolinking, typographer).
 - Configurable syntax! You can add new rules and even replace existing ones.
-- High speed!
+- High speed.
 - Community-written __[plugins](https://www.npmjs.org/browse/keyword/markdown-it-plugin)__ and [other packages](https://www.npmjs.org/browse/keyword/markdown-it) on npm.
 
 __Table of content__