updateList = function (ruleSet, isAtRule, line, col) {
  parentSelector[curLevel] = ruleSet;
  curSelector = {
    selector: helpers.stripLastSpace(parentSelector.join('')),
    line: line,
    column: col
  };
  if (!isAtRule) {
    selectorList.push(curSelector);
  }
}
Traverses a block and calls our callback function for each block encountered

@param {string} ruleSet - The current selector
@param {boolean} isAtRule - Whether the ruleSet is an atRule
@param {string} line - The line that the ruleset starts
@param {string} col - The column that the ruleset starts
@returns {undefined}