code: function List(options) {
    Base.call(this, options || {});
    this.items = [];
    this.define('keyMap', {});
    this.define('Item', this.options.Item || require('./item'));
    this.visit('item', this.options.items || {});
    delete this.options.items;
    mixins(this);
  }
docs: Create an instance of `List` with the given options. Lists are
  arrayified collections, with items that can be sorted, filtered,
  grouped, and paginated. The `List` constructor inherits from Base.
  
  ```js
  var list = new List();
  ```
  
  @param {Object} `options` `List` options (passed to `Base`)
  @return {undefined}
  @api public