code: function andEvaluator(conditions, leafEvaluator) {
    var sawNullResult = false;
    for (var i = 0; i < conditions.length; i++) {
      var conditionResult = evaluate(conditions[i], leafEvaluator);
      if (conditionResult === false) {
        return false;
      }
      if (conditionResult === null) {
        sawNullResult = true;
      }
    }
    return sawNullResult ? null : true;
  }
docs: Evaluates an array of conditions as if the evaluator had been applied
  to each entry and the results AND-ed together.
  @param  {Array}      conditions      Array of conditions ex: [operand_1, operand_2]
  @param  {Function}   leafEvaluator   Function which will be called to evaluate leaf condition values
  @return {?Boolean}                   Result of evaluating the conditions. A return value of null
  indicates that the conditions are invalid or unable to be
  evaluated.