Fix no jump when query begins with - in Zsh

Created by: eepp

Without this commit, the following command prints the path found by autojump, but doesn't actually jump because the Zsh script assumes we're passing an option to j():

j -- -tools

The -- is needed; otherwise -tools would be interpreted as a (bad) autojump option.

The Bash version (and probably others) does the same, but this commit only fixes it for Zsh.