function pick(obj){
  var keys = [].slice.call(arguments, 1);
  var ret = {};

  for (var i = 0, key; key = keys[i]; i++) {
    if (key in obj) ret[key] = obj[key];
  }

  return ret;
}
Pick keys from an `obj`.

@param {Object} obj
@param {Strings} keys...
@return {Object}