constructor(root, options) {
    super(root);
    options = options || {};
    this.hoist = options['hoist atrules'];
    this.stack = [];
    this.map = {};
    this.imports = [];
  }
Initialize a new `Normalizer` with the given `root` Node.

This visitor implements the first stage of the duel-stage
compiler, tasked with stripping the "garbage" from
the evaluated nodes, ditching null rules, resolving
ruleset selectors etc. This step performs the logic
necessary to facilitate the "@extend" functionality,
as these must be resolved _before_ buffering output.

@param {Node} root
@api public