Fix chpwd hook

Using smartcd by chpwd hook in zsh currently only works for the first directory change. 

There is something going wrong within the stash magic, but i was unable to figure out the root cause. I sidestepped this issue by using the `-q` flag for cd to avoid smartcd's chpwd hook handling which i therefore ripped out.

A script in the last commit (not meant for inclusion) demonstrates this problem.