Makes sure that autojump is sourced before running.

For @blueyed, fixes #255.
@wting 
This looks like some merge error!
The options need to be defined before the `cd` (see https://github.com/joelthelion/autojump/issues/312#issuecomment-55961937), and there's a parse error here.
I will test and amend it with the old lines 50-54 removed.