1.04 -- Added PTBmu.gen and PTBmn.gen method for repeated disturbances
	Fixed a bug in PTBu for size<>1
	Minor documentation

1.05
-- Added a framework for discrete perturbations using a reclassification matrix
(PTBdiscrete,reclass.mat.diag)
-- Updated default perturb options to detect discrete variables and
   use appropriate method
-- Added plot method for perturb.summary
-- Added built-in support for perturbing Zelig models and plotting and summarizing
   the results

