Util: add config_directory and config_file_path functions.
Add busybird script (only POD yet). Runner::run() function now has explicit return value spec.
Rename xt/config_path.t -> xt/Util_config_path.t
Implement Runner. not tested yet.
Runner: fix some bugs. Pass the test xt/Runner.t
Implement busybird script.
Some minor bug fixes: Runner: --help option should not take argument. busybird: return value of Runner::run() must be checked for defined-ness, not truth.