Get changelogs from git tags

[alvarogzp]

I think it is a good place to describe some highlights about the new version being tagged, so I use it for my projects (eg. https://github.com/alvarogzp/telegram-bot-framework/releases).

pyupio redirected me here to suggest you how to find the changelog for my telegram-bot-framework package (the one linked above), so that is what I am doing.

I think it shouldn't be too much difficult to add support for getting changelogs from git tag descriptions, and it could also benefit other projects that may do it for their changelogs too!