fix warning: LANG=ja_JP.utf-8 だと warning がでるので LANG=C にする

    perl: warning: Falling back to the standard locale ("C").
    perl: warning: Setting locale failed.
    perl: warning: Please check that your locale settings:
            LANGUAGE = (unset),
            LC_ALL = (unset),
            LANG = "ja_JP.utf-8"
        are supported and installed on your system.
    perl: warning: Falling back to the standard locale ("C").
fix test: mkdir の引数間違えてて warning でていた。orz

    Argument "mkdir(2) should success" isn't numeric in mkdir at t/fixbug-8.t line 12.
add test: chown(2) のテストを追加