Add a nerv example. (#3573)

* Add a nerv example.

* Fix for indentation/style

* Fix for name

examples/using-nerv/README.md

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+[![Deploy to now](https://deploy.now.sh/static/button.svg)](https://deploy.now.sh/?repo=https://github.com/zeit/next.js/tree/master/examples/using-nerv)
+
+# Hello World example
+
+## How to use
+
+### Using `create-next-app`
+
+Download [`create-next-app`](https://github.com/segmentio/create-next-app) to bootstrap the example:
+
+```
+npm i -g create-next-app
+create-next-app --example using-nerv using-nerv-app
+```
+
+### Download manually
+
+Download the example [or clone the repo](https://github.com/zeit/next.js):
+
+```bash
+curl https://codeload.github.com/zeit/next.js/tar.gz/canary | tar -xz --strip=2 next.js-canary/examples/using-nerv
+cd using-nerv
+```
+
+Install it and run:
+
+```bash
+npm install
+npm run dev
+```
+
+Deploy it to the cloud with [now](https://zeit.co/now) ([download](https://zeit.co/download))
+
+```bash
+now
+```
+
+## The idea behind the example
+
+This example uses [Nerv](https://nerv.aotu.io/) instead of React. It's a "blazing fast React alternative, compatible with IE8 and React 16". Here we've customized Next.js to use Nerv instead of React.
+
+Here's how we did it:
+
+* Use `next.config.js` to customize our webpack config to support [Nerv](https://nerv.aotu.io/)

examples/using-nerv/next.config.js

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+module.exports = {
+  webpack: function (config, { dev }) {
+    // For the development version, we'll use React.
+    // Because, it supports react hot loading and so on.
+    if (dev) {
+      return config
+    }
+
+    config.resolve.alias = {
+      react: 'nervjs',
+      'react-dom': 'nervjs'
+    }
+
+    return config
+  }
+}

examples/using-nerv/package.json

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+{
+  "name": "using-nerv",
+  "version": "1.0.0",
+  "scripts": {
+    "dev": "node server.js",
+    "build": "next build",
+    "start": "NODE_ENV=production node server.js"
+  },
+  "dependencies": {
+    "module-alias": "^2.0.0",
+    "next": "latest",
+    "nervjs": "^1.2.4",
+    "react": "^16.0.0",
+    "react-dom": "^16.0.0"
+  },
+  "license": "ISC",
+  "devDependencies": {
+    "react": "~15.6.1",
+    "react-dom": "~15.6.1"
+  }
+}

examples/using-nerv/pages/about.js

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+import React from 'react'
+
+export default () => (
+  <div>About us</div>
+)

examples/using-nerv/pages/index.js

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+import React from 'react'
+import Link from 'next/link'
+
+export default () => (
+  <div>Hello World. <Link href='/about'><a>About</a></Link></div>
+)

examples/using-nerv/server.js

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+const port = parseInt(process.env.PORT, 10) || 3000
+const dev = process.env.NODE_ENV !== 'production'
+const moduleAlias = require('module-alias')
+
+// For the development version, we'll use React.
+// Because, it support react hot loading and so on.
+if (!dev) {
+  moduleAlias.addAlias('react', 'nervjs')
+  moduleAlias.addAlias('react-dom', 'nervjs')
+}
+
+const { createServer } = require('http')
+const { parse } = require('url')
+const next = require('next')
+
+const app = next({ dev })
+const handle = app.getRequestHandler()
+
+app.prepare()
+.then(() => {
+  createServer((req, res) => {
+    const parsedUrl = parse(req.url, true)
+    handle(req, res, parsedUrl)
+  })
+  .listen(port, (err) => {
+    if (err) throw err
+    console.log(`> Ready on http://localhost:${port}`)
+  })
+})