code: function salute (cb) {
    return (req, res, ...args) => {
      var value = null
      try {
        value = cb(req, res, ...args) || ''
      } catch (e) {
        value = e
      }
      return stream(Promise.resolve(value).then(type(res)))
        .on('error', status(res))
    }
  }
docs: Create an HTTP request/response middlware which
  chunk any type of value returned as well as set
  the response content type.
  
  @param {Function} cb
  @api public