docs: function Timetraveller (map, timeline, options) {
    var self = this
  
    this.map = map
    this.id = document.getElementById('map').dataset.id
    this.slug = document.getElementById('map').dataset.slug
    this.markers = {}
    this._elements = {
      clock: [],
      speed: [],
      play: [],
      stop: []
    }
    this._options = options || {}
  
    this._timeline = timeline
  }