test, and fix, symlink traversal in [GatherDir]
also test a dotted directory that is not the top level directory
deal with Path::Tiny objects internally, for a bit more sanity
add some debug logging indicating the path we are considering gathering
use File::Find::Rule for filtering dotfiles
use File::Find::Rule to skip the exclude_filename files
use File::Find::Rule to skip the exclude_match files
this order now makes more sense
add "prune_directory" option to [GatherDir]