code: function differenceKeys(first, second) {
      return filterKeys(first, function(val, key) {
          return val !== second[key];
      });
  }
docs: Gets indices for which elements differ between two arrays.
  
  @static
  @memberOf _
  @category Collection
  @param {array} first First array
  @param {array} second Second array
  @return {array} Array of indices of differing elements
  @example
  
  _.differenceKeys([false, true], [false, false]);
  // => [1]