collection>filtered/refactor: base off of derivedlist; fix remove bug.
templater/rm: kill off RenderWith mutator.
binder/bug: should discard previously rendered views before empty().
varying/new: new "lie" api for lying non-nefariously to the user.

* initially, a `sticky` liar to make values stay for longer. useful
  if you want a message to persist for only a couple seconds past
  its relevance.