message: docs: add badge in readme
diff: ZRender
  =======
  -A lightweight canvas library which providing 2d draw for [ECharts](https://github.com/ecomfe/echarts)
  +A lightweight canvas library which providing 2d draw for [ECharts](https://github.com/ecomfe/echarts).
  +
  +[![Build Status](https://travis-ci.com/ecomfe/zrender.svg?branch=master)](https://travis-ci.com/ecomfe/zrender) [![](https://img.shields.io/npm/dw/echarts.svg?label=npm%20downloads&style=flat)](https://www.npmjs.com/package/echarts) ![Commits Since 4.0.0](https://img.shields.io/github/commits-since/apache/incubator-echarts/4.0.0.svg?colorB=%234c1&style=flat)
  ## Document
  