##change / RobustCalibration 0.5.2
* code maximum likelihood estimator by argument "method" in rcalibration and rcalibration_MS
* ppgasp function from RobustGaSP package is called for emulating expensive simulator with vectorized output
* allow user to specify replications specifying different types of observations in rcalibration 
* introduce a default scaling parameter lambda_z in rcalibration, rcalibration_MS

## change / RobustCalibration 0.5.1
  * fixed the bug (appearing on line line 147 in rcalibration()) with an emulator.
  * created rcalibration_MS() and rcalibration_MS class for calibrating mathematical models for multiple sources.
  * created predict_MS() for prediction after calibrating mathematical models
  * created predictobj.rcalibration and predictobj.rcalibration_MS classes for the output for the predict() and predict_MS() function