v0.9 : stuff to add
  fix crappy description
  categorical variable detection/use
    cleanup old array of bools vs. bits in a uint
    check that using values of uints hiding w/in doubles makes sense
  warn on possible factors
  change and swap rule variable names
  change and swap rule encapsulation
    unify node state store/restore
  "functions" getting a better organizing principle
  general encapsulation of node implementation
  look into speed change in tracking variables avail for split
  cleanup pthreads
  pdbart/pdbart2
  causal
  predict
  move n.eff cached calculation into scratch
  handle updating y for binary better w/r/t latents

v1.0 : cleanup, bug fixes
  rethink model/prior interface
  thread cancellation
  check bounds on parameters for CGM prior
  verify that all of state is necessary to store
  unify R coding style to ALL caps or not
  consistency of error message style