code: function getCssSelectorClasses(selector) {
    var list = []
    var ast = cssSelector.parse(selector)
    visitRules(ast, function(ruleSet) {
      if (ruleSet.classNames) {
        list = list.concat(ruleSet.classNames)
      }
    })
    return uniq(list)
  }
docs: Return all the classes in a CSS selector.
  
  @param {String} selector A CSS selector
  @return {String[]} An array of every class present in the CSS selector