Fetch missing versions and `amend` them to existing change log

This is sub-task of #209.
Depends of #212
Needed to implement partial update of the `CHANGELOG.md`. i.e. fetch only specific issues (between specific tags, or between time) and not modify others records. i.e. kind of `--amend` command in `git`.

This will be a great workaround and fix #71.
