0.4.1

Required for git version 2.21 and higher.

• Fix Bash version error messages and add to .rc
• Nicer YAML formatting in .travis.yml
• Wrap a long line
• Update the docs
• Force make update to always update docs
• Don't use XXX in perl stuff
• Add testing on MacOS
• Remove conflicting -C from install -d commands.
• Update version requirement documentation
• Correct error message in branch
• Use topo-order in subrepo branch
• Make “git subrepo clean -f ...” delete refs correctly
• Fix #410 Push empty repositories with recent git versions
• Make subrepo work when run in a worktree
• Simplify finding subrepos
• Ask git to find the .gitrepo files
• Doc: fix sentence repetition
• Fix typos
• Fixed typo
• Travis CI not checking out a branch.