* Remove .travis.yml files from galaxy init skeletons
These files have existed for many years but in light of the recent
circumstances around Travis, we should not include them by default in
the galaxy init skeletons.
* Add breaking_changes changelog fragment with recommendation to use a custom skeleton if the .travis.yml file is still needed.
Co-authored-by: s-hertel <19572925+s-hertel@users.noreply.github.com>