code: function retrieve(uri, callback) {
    var buffer = '';
    http.get(uri, function(res) {
      res.on('data', function (chunk) {
        buffer += chunk;
      });
      res.on('end', function() {
        callback(null, buffer);
      });
    }).on('error', function(e) {
      callback(e);
    });
  }
docs: perform a GET then callback content