Changelog for the curriculums

[mhalano]

The idea here is to provide together with the curriculum PDF a changelog about the items that were changed, at least from the previous version to the latest, but ideally for more versions. This could help people, like me, that are studying with older courses that could take too much time to update, so we can use the older course and study the new additions by ourselves.

[aungzanbaw]

That's why we are talking about it in #69, if we could compare side by side(old vs new) that would be helpful for new comers.