function sortedIndexTwo (array, obj, iterator, context) {
  var low = 0, high = array.length;
  while (low < high) {
    var mid = (low + high) >>> 1;
    iterator.call(context, obj, array[mid]) > 0 ? low = mid + 1 : high = mid;
  }
  return low;
}
Equivalent to _.sortedIndex, but for comparators with two arguments