message: Update README.md
  added CircleCI badge
diff: <img src="https://github.com/remult/remult/raw/master/docs/.vuepress/public/logo.png" width="140" height="140">
  </a>
  <h1>Remult</h1>
  + <a href="https://circleci.com/gh/remult/remult/tree/master">
  + <img alt="CircleCI" src="https://circleci.com/gh/remult/remult/tree/master.svg?style=svg">
  + </a>
  <a href="https://raw.githubusercontent.com/remult/remult/master/LICENSE">
  <img alt="GitHub license" src="https://img.shields.io/badge/license-MIT-blue.svg">
  </a>
  