code: function trailer(file, fn) {
    return through({objectMode: true}, function (a, e, cb) {
      this.push(a)
      cb()
    }, function (cb) {
      var self = this
      fn(function (err, val) {
        if (err) { return cb(err) }
        if (val) {
  
          if (typeof val === 'string') {
            val = new Buffer(string)
          }
          
          var f = new File({
            path: file,
            contents: val
          })
  
          self.push(f)
        }
        cb()  
      })
      
    })
  }
docs: attempt to send another obj in the stream at the end