html.js

import React from 'react'
import Helmet from 'react-helmet'

import { prefixLink } from 'gatsby-helpers'
import { TypographyStyle, GoogleFont } from 'react-typography'
import typography from './utils/typography'

const BUILD_TIME = new Date().getTime()

module.exports = class Html extends React.Component {

    render () {
        const head = Helmet.rewind()

        let css
        if (process.env.NODE_ENV === 'production') {
            css = <style dangerouslySetInnerHTML={{ __html: require('!raw!./public/styles.css') }} />
        }

        return (
            <html lang="en">
              <head>
              <script type="text/javascript" async src="https://cdn.mathjax.org/mathjax/latest/MathJax.js?config=TeX-MML-AM_CHTML"/>
              <script async src="//platform.twitter.com/widgets.js" charset="utf-8"></script>
              <meta charSet="utf-8" />
              <meta httpEquiv="X-UA-Compatible" content="IE=edge" />
              <meta name="viewport" content="width=device-width, initial-scale=1.0" />
              { head.title.toComponent() }
              { head.meta.toComponent() }
              <TypographyStyle typography={typography} />
              <GoogleFont typography={typography} />
              { css }
            </head>
            <body>
              <div id="react-mount" dangerouslySetInnerHTML={{ __html: this.props.body }} />
              <script src={prefixLink(`/bundle.js?t=${BUILD_TIME}`)} />
            </body>
            </html>
        )
    }
};