Revert "Remove rubocop platforms which are not valid on older deb OSes"

This reverts commit 79d915ac1901061ab6dc0225318d9738a1b11ead.

The Gemfile has been altered upstream to not use :platforms, so this is
safe to drop
Update to hammer_cli 0.1.3 and hammer_cli_foreman 0.1.3
Add utility to add changelog entries