caretStack: Combine several predictive models via stacking

if (FALSE) {
library("rpart")
models <- caretList(
  x=iris[1:50,1:2],
  y=iris[1:50,3],
  trControl=trainControl(method="cv"),
  methodList=c("rpart", "glm")
)
caretStack(models, method="glm")
}