code: function HTTPTracker (client, announceUrl, opts) {
    var self = this
    Tracker.call(self, client, announceUrl)
    debug('new http tracker %s', announceUrl)
  
    // Determine scrape url (if http tracker supports it)
    self.scrapeUrl = null
  
    var match = self.announceUrl.match(HTTP_SCRAPE_SUPPORT)
    if (match) {
      var pre = self.announceUrl.slice(0, match.index)
      var post = self.announceUrl.slice(match.index + 9)
      self.scrapeUrl = pre + '/scrape' + post
    }
  
    self.cleanupFns = []
    self.maybeDestroyCleanup = null
  }
docs: HTTP torrent tracker client (for an individual tracker)
  
  @param {Client} client       parent bittorrent tracker client
  @param {string} announceUrl  announce url of tracker
  @param {Object} opts         options object