code: function renameSelector(selector, sourcePath, opts, mappings) {
    return selector.map(function(selector){
      return parser(function(sels) {
        sels.map(function(sel) {
          renameNodes(sel.nodes, sourcePath, opts, mappings);
        })
      }).process(selector).result
    });
  }
docs: Renames all classnames in a css rule selector
  @param selector css selector
  @param sourcePath Source file's path
  @param opts Options object
  @param mappings Classname to renamed classname mappings repository
  @return {*} Renamed css rule selector