removed dorky printf debug
Fixed .remove() api.
Now it is like leaf.remove api; it takes only a key and returns a deleted
child value (a handle). aka `hdl = br.remove(key)`.
changed constructor argument to #ms of delay; -1 for nodelay
implemented choice of MemStore or TrivialStore & some output tweaks
several changes
- removed alot of printf-debugging aka `console.warn` messages
- changed api from passing (newHdls, oldHlds) around to just deadHdls
- made .cleanHandles() work. problem was some .storeSimplePath calles would
  not progress to root. Put .cleanHandles() call in where .storeSimplePath
  gives up on walking up the path chain.