Thanks to the following people:

  Whit Armstrong <Whit.Armstrong@tudor.com>
  - information on model.frame

  Matthieu Cormec <matthieu.cormec@gmail.com>
  - testing

  Roger Koenker <rkoenker@uiuc.edu>
  - quantreg::rq upgrade and testing

  Andy Liaw <andy_liaw@merck.com>
  - randomForest upgrade

  Achim Zeileis <Achim.Zeileis@wu-wien.ac.at>
  - discussions on zoo
  - packaging information

