Implemented ensemble selection to construct an ensemble of models in the output of gbts().
Revised the API of gbts() to simplify the specification of minimum and maximum values of hyperparameters.
Improved the display of optimization progress.
Terminated support for the R package "xgboost".
Modified access to gbm predict() to be compatible with the current and next version of gbm.
Revised the documentation of gbts() and the DESCRIPTION file to describe Bayesian optimization in replacement of active learning. This is merely a documentation change for the same algorithm.
Allowed the "srch" argument of gbts() to accept "bayes" for Bayesian optimization.
Revised the description of the "cutoff" argument of gbts().
Changed R (>= 3.3.1) in the DESCRIPTION file to R (>= 3.3.0) to address the installation error from OS X on CRAN, which uses R version 3.3.0 at the time.