issue #23 implemented

Some notes:
Container `std::map` is not very well suited for iteration php array. Since when inserting it orders keys. Thereby lost the original ordering of the array ( which is very often is important ) .
I think it's better to use the serial container such as `std::vector` or `std::list` ( or `std::forward_list`). In general, that `std::vector` — would fit perfectly .
In the container, you can store simple objects similar, `std::pair`. Only instead *first* and *second* to make *key* and *value*.
As a bonus, we get instead
```c
for (auto &i: m) {
    std::cout << "key:" << i.first << "\t\t val:" << i.second << std::endl;
}
```
here it is
```c
for (auto &i: m) {
    std::cout << "key:" << i.key << "\t\t val:" << i.value << std::endl;
}
```
That looks better with the approach practiced in the library.