Prepare to release 3.0, update readme, add doc-zh link.

README.md

-Sky Walking
+Sky Walking | [中文](https://github.com/wu-sheng/sky-walking/wiki/sky-walking-documents-zh-contents)
 ==========
 
 <img src="https://sky-walking.github.io/page-resources/3.0/skywalking.png" alt="Sky Walking logo" height="90px" align="right" />
@@ -11,10 +11,11 @@ Sky Walking
 [![codebeat badge](https://codebeat.co/badges/579e4dce-1dc7-4f32-a163-c164eafa1335)](https://codebeat.co/projects/github-com-wu-sheng-sky-walking)
 [![Join the chat at https://gitter.im/sky-walking/Lobby](https://badges.gitter.im/sky-walking/Lobby.svg)](https://gitter.im/sky-walking/Lobby?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge)
 [![OpenTracing-1.0 Badge](https://img.shields.io/badge/OpenTracing--1.0-enabled-blue.svg)](http://opentracing.io)
-[![Release Version](https://img.shields.io/badge/tesing-3.0--2017-yellow.svg)](https://github.com/wu-sheng/sky-walking/releases)
+[![Release Version](https://img.shields.io/badge/release-3.0--2017-yellow.svg)](https://github.com/wu-sheng/sky-walking/releases)
 
 
 * Auto-instrumentation mechanism, **no need to CHANGE any application source code**. [Supported middlewares, frameworks and libraries](https://github.com/wu-sheng/sky-walking/wiki/3.0-supported-list).
+* Explicit-instrumentation, by implement OpenTracing supported tracer.
 * Pure Java server implementation, with RESTful Web service.
 * High performance streaming analysis.
 * The UI released on [wu-sheng/sky-walking-ui](https://github.com/wu-sheng/sky-walking-ui)