Added last working directory plugin

Keeps track of the last changed directory. When a new shell is created,
the last directory will be restored. Mimics how tabs works in many
terminal emulators.

plugins/last-working-dir/last-working-dir.plugin.zsh

+#!/usr/bin/env zsh
+# Keeps track of the last used working directory and automatically jumps
+# into it for new shells.
+
+# Flag indicating if we've previously jumped to last directory.
+typeset -g ZSH_LAST_WORKING_DIRECTORY
+local cache_file="$ZSH/cache/last-working-dir"
+
+# Updates the last directory once directory is changed.
+function chpwd() {
+	echo "$PWD" > "$cache_file"
+}
+
+# Changes directory to the last working directory.
+function lwd() {
+	[[ ! -r "$cache_file" ]] || cd `cat "$cache_file"`
+}
+
+# Automatically jump to last working directory unless this isn't the first time
+# this plugin has been loaded.
+if [[ -z "$ZSH_LAST_WORKING_DIRECTORY" ]]; then
+	lwd 2>/dev/null && ZSH_LAST_WORKING_DIRECTORY=1 || true
+fi