Add permalink

[403studio]

Add permalink to docs, so we can access with 'prev' and 'next'
without it we can only access this doc use http://facebook.github.io/react/docs/**tutorial.zh-CN.html**
however in the file which named getting-start.zh-CN.md has designed like this:

---
id: getting-started-zh-CN
title: 入门教程
permalink: getting-started-zh-CN.html
next: tutorial-zh-CN.html
redirect_from: "docs/index-zh-CN.html"

---

[ghost]

Thank you for your pull request and welcome to our community. We require contributors to sign our Contributor License Agreement, and we don't seem to have you on file. In order for us to review and merge your code, please sign up at https://code.facebook.com/cla - and if you have received this in error or have any questions, please drop us a line at cla@fb.com. Thanks!

[403studio]

Signed CLA @facebook-github-bot-4

[ghost]

Thank you for signing our Contributor License Agreement. We can now accept your code for this (and any) Facebook open source project. Thanks!

[jimfb]

Ok, thanks!