Simplify interface for emoticon.py

emoticon.py now serves a single purpose: generating training and
testing data. Additionally, instead of creating a 60/20/20 train,
dev, and test split, emoticon.py now creates a 60/40 train and test
split. The composition of each subset is randomized, as before.
classify.py returns better accuracy metrics

returns false positive rate, false negative rate, and
overall accuracy