Introduced trainStrategy

decoder/include/Beam.hpp

decoder/src/Beam.cpp

reading_machine/include/ReadingMachine.hpp

reading_machine/src/ReadingMachine.cpp

torch_modules/src/ConfigDataset.cpp

trainer/include/MacaonTrain.hpp

trainer/include/Trainer.hpp

trainer/src/MacaonTrain.cpp

trainer/src/Trainer.cpp