Use Path::Tiny instead of Path::Class
    
  Merging github#16 by Kent Fredric
Document allow_dirty_match in Role::Git::DirtyFiles

  Requested by Karen Etheridge
v2.020

 - convert from Path::Class to Path::Tiny (kent fredric - github#16)
 - better documentation for allow_dirty_match (christopher madsen,
   requested by karen etheridge)
Git::Commit: Ensure add_files_in is an ArrayRef[Path] to force validation at initialization