mutate.training_frame: add default changed to FALSE
train_grouping utils added
as.grouped_training_frame added
code re-formatted
doc update
of predictors aren't specified they are taken to be all columnns not equal to the target or the training group columns
fit => validate
additional utils added
class of modelling frame printed
noted added for [.modelling_frame
filter.grouped_testing_frame method deprecated
train method added for a grouped training frame
predict method added for a grouped model
doc update
code reformatted