Adding find-fn-for-pred

[arosequist]

There are times when I want to find a fn that returns a value that matches a predicate other than equality ("find a fn that returns an empty seq (of any type)" or "find a fn that returns something that implements this protocol").

This adds a function called find-fn-for-pred (any suggestions on a name?) that takes a predicate rather than a value for the out, and re-implements find-fn using this new function.