starting work on multiclass classifiers

+ moving the "adhoc jobs" into scala from java (they were misplaced before)
+ adding adhoc multiclass classifier
+ making multiclass instances from TextSequence
agree. This is something clynch added. I'll move things over to here: https://github.com/etsy/Conjecture/blob/master/src/main/scala/com/etsy/conjecture/scalding/train/BinaryModelTrainer.scala#L80