Revert "[#129, #211] Remove z"

This reverts commit b967c50faf.

.gitmodules

@@ -7,3 +7,6 @@
 [submodule "modules/completion/external"]
 	path = modules/completion/external
 	url = https://github.com/zsh-users/zsh-completions.git
+[submodule "modules/z/external"]
+	path = modules/z/external
+	url = https://github.com/rupa/z.git

modules/z/README.md

@@ -0,0 +1,21 @@
+Z
+=
+
+Integrates [z][1] into Prezto, which maintains a frequently used directory
+list for fast directory changes.
+
+Aliases
+-------
+
+  - `j` changes the current working directory to the most *frecent* match.
+
+Authors
+-------
+
+*The authors of this module should be contacted via the [issue tracker][2].*
+
+  - [Sorin Ionescu](https://github.com/sorin-ionescu)
+
+[1]: https://github.com/rupa/z
+[2]: https://github.com/sorin-ionescu/prezto/issues
+

modules/z/external

@@ -0,0 +1 @@
+Subproject commit 9bf5feb86ac05ad32cd8fbf46d459eb415eed749

modules/z/init.zsh

@@ -0,0 +1,19 @@
+#
+# Maintains a frequently used directory list for fast directory changes.
+#
+# Authors:
+#   Sorin Ionescu <sorin.ionescu@gmail.com>
+#
+
+# Set the directory changing command.
+_Z_CMD='j'
+
+# Prevent symbolic link resolution.
+_Z_NO_RESOLVE_SYMLINKS=1
+
+# Source module files.
+source "${0:h}/external/z.sh"
+
+# Cleanup.
+unset _Z_{CMD,NO_RESOLVE_SYMLINKS}
+