Replace inheritance from std::iterator

[elshize]

std::iterator was deprecated in C++17. It should be replaced by explicitly defining iterator traits. More details here: https://www.fluentcpp.com/2018/05/08/std-iterator-deprecated/https://www.fluentcpp.com/2018/05/08/std-iterator-deprecated/

I noticed it when my compiler started throwing warnings at me around the binary collection code; but there might be more instances, we should double-check.