Rethink implementation of `z`.
Rethink implementation of `z`.

Since bash completion is tricky to get and original bash completion code
implementation relied on commands being an alias, `fasd_cd` is
introduced as an intermediate to `z`. This also helps if users want to
use other alias for `fasd -e cd -d`.

clvv/fasd,dankilman/fasd,Vifon/fasd,allcatsarebeautiful/fasd,Neki/fasd,alphapapa/fasd