use direct service badges (shields.io is unstable)

Author: yyx990803

README.md

@@ -1,11 +1,10 @@
 <p align="center"><a href="http://vuejs.org" target="_blank"><img width="100"src="http://vuejs.org/images/logo.png"></a></p>
 
 <p align="center">
-  <a href="https://circleci.com/gh/yyx990803/vue/tree/master"><img src="https://img.shields.io/circleci/project/yyx990803/vue/master.svg" alt="Build Status"></a>
-  <a href="https://codecov.io/github/yyx990803/vue?branch=master"><img src="https://img.shields.io/codecov/c/github/yyx990803/vue/master.svg" alt="Coverage Status"></a>
+  <a href="https://circleci.com/gh/yyx990803/vue/tree/master"><img src="https://circleci.com/gh/yyx990803/vue/tree/master.svg?style=shield" alt="Build Status"></a>
+  <a href="https://codecov.io/github/yyx990803/vue?branch=master"><img src="https://codecov.io/github/yyx990803/vue/coverage.svg?branch=dev" alt="Coverage Status"></a>
   <a href="https://www.bithound.io/github/yyx990803/vue"><img src="https://www.bithound.io/github/yyx990803/vue/badges/score.svg" alt="bitHound Score"></a>
   <br>
-  <a href="https://www.npmjs.com/package/vue"><img src="https://img.shields.io/npm/dm/vue.svg" alt="NPM Downloads"></a>
   <a href="http://issuestats.com/github/yyx990803/vue"><img src="http://issuestats.com/github/yyx990803/vue/badge/issue?style=flat"></a>
 </p>