1.7.2: improve bash / zsh shell compatibility

Author: skywind3000

z.lua

@@ -4,7 +4,7 @@
 -- z.lua - a cd command that learns, by skywind 2018, 2019
 -- Licensed under MIT license.
 --
--- Version 1.7.1, Last Modified: 2019/06/07 22:07
+-- Version 1.7.2, Last Modified: 2019/08/01 19:45
 --
 -- * 10x faster than fasd and autojump, 3x faster than z.sh
 -- * available for posix shells: bash, zsh, sh, ash, dash, busybox