Add a RecurrentNeuralNetworkPartOfSpeechTagger class.
Remove trailing whitespace.
Rename pos_tagger to part_of_speech_tagger in Evaluator.
Use the RecurrentNeuralNetworkPartOfSpeechTagger in main().
Use override annotation in DumbPartOfSpeechTagger.
Make layers take multiple input and output variables,
so that they better match morphisms in category theory.