title: How to use webtorrent in browser？
body: <p>I have some trouble with the the example showed in <a href="https://github.com/feross/webtorrent#usage" rel="noreferrer">https://github.com/feross/webtorrent#usage</a>
  I'm trying to use the code in browser. So I first create a file called app.js</p>
  
  <p><strong>app.js</strong></p>
  
  <pre><code>var WebTorrent = require('webtorrent')
  var concat = require('concat-stream')
  
  var client = new WebTorrent()
  console.log('Hi there');
  client.download('magnet:?xt=urn:btih:XXXXXXXX', function (torrent) {
    // Got torrent metadata!
    console.log('Torrent info hash:', torrent.infoHash)
  
    torrent.files.forEach(function (file) {
      // Get the file data as a Buffer (Uint8Array typed array)
      file.createReadStream().pipe(concat(function (buf) {
  
        // Append a link to download the file
        var a = document.createElement('a')
        a.download = file.name
        a.href = URL.createObjectURL(new Blob([ buf ]))
        a.textContent = 'download ' + file.name
        document.body.appendChild(a)
      }))
    })
  })
  </code></pre>
  
  <p>Then I type command <code>browserify app.js &gt; bundle.js</code> so that can make code work for browser. I create another file called index.html:</p>
  
  <p><strong>index.html</strong></p>
  
  <pre><code>&lt;!DOCTYPE html&gt;
  &lt;html lang="en"&gt;
  &lt;head&gt;
      &lt;meta charset="utf-8"&gt;
      &lt;title&gt;test&lt;/title&gt;
      &lt;script src="bundle.js"&gt;&lt;/script&gt;
  &lt;/head&gt;
  
  &lt;body id="home"&gt;
  
      &lt;h1&gt;test&lt;/h1&gt;
  
  
  &lt;/body&gt;
  &lt;/html&gt;
  </code></pre>
  
  <p>From the console I can only see "Hi there". It seems that the client.download() function didn't work. Why this happened? I'm new to browserify, is there anything wrong with the command which I use?</p>