Reimplement version module in C++

After talking to Allan I have started to re-implement `version` module in C++. Here is little road map that might change at any time, depending on what kind of results we are going to collect:

- [x] re-implement `NumericToken`, `AlphanumericVersionToken` in `C++`.
- [x] expose `NumericToken`, `AlphanumericVersionToken` through `pybind` as `Python` module.
- [ ] swap`Python`'s implementation with `NumericToken` and `AlphanumericVersionToken` exposed through `pybind`.
- [ ] benchmark `Python` and `pybind` tokens.
- [ ] re-implement `Version` in `C++`.
- [ ] Mechanism to switch between compiled and python version