message: remove styled-components static CSS rendering
diff: import React from 'react'
  import Document, {Head, Main, NextScript} from 'next/document'
  -import {ServerStyleSheet} from 'styled-components'
  export default class MyDocument extends Document {
  - static getInitialProps({renderPage}) {
  - const sheet = new ServerStyleSheet()
  - const page = renderPage(App => props => sheet.collectStyles(<App {...props} />))
  - const styles = sheet.getStyleElement()
  - return {...page, styles}
  - }
  -
  render() {
  const {
  - styles,
  - // this comes from the app.setAssetPrefix() call in server.js
  + // the assetPrefix is set in next.config.js
  __NEXT_DATA__: {assetPrefix = ''}
  } = this.props
  @@ -29,10 +20,8 @@ export default class MyDocument extends Document {
  {/* See: https://github.com/zeit/next-plugins/tree/master/packages/next-sass#usage */}
  <link rel="stylesheet" href={asset('/_next/static/style.css')} />
  <meta name="viewport" content="width=device-width,initial-scale=1" />
  - <meta name="generator" content="Compositor X0" />
  <meta name="og:title" content="Primer React" />
  <meta name="description" content="Primer components built with React.js." />
  - {styles}
  </Head>
  <body>
  <Main />
  