update gemspec to yard 0.6.2 for kramdown support
update gemspec to yard 0.6.2 for kramdown support

robertwahler/mutagem,robertwahler/basic_app,robertwahler/revenc,robertwahler/basic_gem,robertwahler/win32-autogui,robertwahler/oct,robertwahler/dynabix,robertwahler/repo_manager,robertwahler/repo_manager