Add find-parent-dir pkg to .travis.yml
Do raco pkg install --link.

This exercises installing the packages on which it depends (and uses
the list from info.rkt rather than duplicating that list here, too).

It also includes a raco make & link in the bargain.
Fix commit e7429c4f: .travis.yml must install deps, after all.
Fix commit e7429c4f -- again.

Add back raco link and raco make.
Fix raco make
Update THANKS.md