Add tilingaware plugin

Add plugin to save the present working directory over different zsh
sessions. The last change in directory will be preserved.

Add `chpwd' function to change the directory new shells will be opened
in.

plugins/tilingaware/tilingaware.plugin.zsh

@@ -0,0 +1,10 @@
+DIRSTACKSIZE=9
+DIRSTACKFILE=~/.zdirs
+if [[ -f $DIRSTACKFILE ]] && [[ $#dirstack -eq 0 ]]; then
+	dirstack=( ${(f)"$(< $DIRSTACKFILE)"} )
+	[[ -d $dirstack[1] ]] && cd $dirstack[1]
+fi
+
+function chpwd() {
+	print -l $PWD ${(u)dirstack}> $DIRSTACKFILE
+}