code: function bin(argv) {
    var uri = argv[2]
    if (!uri) {
      console.error('uri is required')
    }
    shell.ls(uri, function(err, arr) {
      for (i=0; i<arr.length; i++) {
        console.log(arr[i])
      }
    })
  }
docs: list the contents of a directory
  @param  {[type]} argv [description]
  @return {[type]}      [description]