Backup only the `User` folder

> I know this pull request is closed and merged, but the prefered way to sync settings and packages in Sublime Text 3 changed a bit: https://sublime.wbond.net/docs/syncing "The proper solution is to sync only the Packages/User/ folder"

[Source](https://github.com/lra/mackup/pull/14#issuecomment-31570790)
Merge branch 'fix-support-sublime-text-3' of https://github.com/laupiFrpar/mackup into laupiFrpar-fix-support-sublime-text-3
Added change log entry for improving sublime3 support