update badge color to green (#4777)

Author: coocood

README.md

@@ -2,7 +2,7 @@
 
 [![Build Status](https://travis-ci.org/pingcap/tidb.svg?branch=master)](https://travis-ci.org/pingcap/tidb)
 [![Go Report Card](https://goreportcard.com/badge/github.com/pingcap/tidb)](https://goreportcard.com/report/github.com/pingcap/tidb)
-![Project Status](https://img.shields.io/badge/version-1.0.0-yellow.svg)
+![Project Status](https://img.shields.io/badge/version-1.0-green.svg)
 [![CircleCI Status](https://circleci.com/gh/pingcap/tidb.svg?style=shield)](https://circleci.com/gh/pingcap/tidb)
 [![Coverage Status](https://coveralls.io/repos/github/pingcap/tidb/badge.svg?branch=master)](https://coveralls.io/github/pingcap/tidb?branch=master)