Add divert? functions

[bn-darindouglass-zz]

Bringing in context from Slack:

Some background: for one of our kstreams apps we have a util function call divert? that'll push off a record if a given predicate is true (i.e. to a failure topic, etc):

(defn divert? [stream pred topic]
  (let [[divert-stream continue-stream] (j/branch stream [pred (constantly true])]
    (j/to divert-stream topic)
    continue-stream)

This abstraction, IMO, would feel really good in the library proper because it provides a useful layer on top of j/branch to handle what i'd think is a common use-case (again, failure topics, etc);

[mt3593]

Looks like a dup of #238