reverting multiple-promise-bind to NOT use destructuring-bind. its wayy too rigid for our purposes. the old method may be cludgy, but it works great and im sick of fiddling with it.
using multiple-promise-bind for :then/:attach in chain because its more resilient to things like (chain (values 1 2) (:then (x) (format t "x is ~a~%" x))) which would have thrown an error before this commit (2 args given, 1 accepted, etc etc etc).