Prevent to learn parameters when a condition has less than 1 sample

On this merge request I made the following changes: Prevent to have a condition with less than 2 samples (related to #1 (closed) ) Keep the dimension when subseting (Just in case) Removing unnecessary dependency (There was a package that was imported but was not used) Use message instead of cat to report to the user (Also removing a number being printed)

Hope it can be merged and many thanks for maintaining the package.