Ported 'Walk' method from filepath package.
Ported 'Walk' method from filepath package.

syohex/the_platinum_searcher,monochromegane/the_platinum_searcher,cmars/tools,DaSea/the_platinum_searcher,cmars/tools,cmars/tools,thomasf/the_platinum_searcher,tw4452852/the_platinum_searcher,aeruder/the_platinum_searcher,drmohundro/the_platinum_searcher,cmars/tools,yuya-takeyama/the_platinum_searcher