code: function(fieldName, toggleDirection) {
                  var direction = toggleDirection ? 0 - this.state.order : this.state.order;
                  if (fieldName !== this.state.sortKey || toggleDirection) {
                      this.setSorting(fieldName, direction);
                      this.isStale = true;
                  }
              }
docs: Sets the field to sort on and marks the collection as
  stale.
  
  @param fieldName {string} name of the field to sort on
  @param toggleDirection {boolean} if true, the sort direction is
  toggled if the given field was already set