code: function getElements () {
      var elements = {};
      var node = $element[0];
  
      // gather tab bar elements
      elements.wrapper = node.querySelector('md-tabs-wrapper');
      elements.canvas  = elements.wrapper.querySelector('md-tabs-canvas');
      elements.paging  = elements.canvas.querySelector('md-pagination-wrapper');
      elements.inkBar  = elements.paging.querySelector('md-ink-bar');
      elements.nextButton = node.querySelector('md-next-button');
      elements.prevButton = node.querySelector('md-prev-button');
  
      elements.contents = node.querySelectorAll('md-tabs-content-wrapper > md-tab-content');
      elements.tabs    = elements.paging.querySelectorAll('md-tab-item');
      elements.dummies = elements.canvas.querySelectorAll('md-dummy-tab');
  
      return elements;
    }
docs: Getter methods 
  Gathers references to all of the DOM elements used by this controller.
  @returns {Object}