old_contents: class PublicTagsAPIService {
      constructor(publicAPIRoute) {
          this.publicAPIRoute = publicAPIRoute;
      }
  
      getPopularTags() {
          return this.publicAPIRoute('tags').one('popular').getList().then(
              (tags) => tags.plain()
          );
      }
  }
  
  angular.module('materialscommons').service('publicTagsAPI', PublicTagsAPIService);
  
new_contents: class PublicTagsAPIService {
      constructor(Restangular) {
          this.Restangular = Restangular;
      }
  
      getPopularTags() {
          return this.Restangular.one('v3').one('getPopularTagsForPublishedDatasets').customPOST().then(
              (tags) => tags.plain().data
          );
      }
  }
  
  angular.module('materialscommons').service('publicTagsAPI', PublicTagsAPIService);
  
subject: Switch to actionhero based API