Enable passing args to tf.k.Model.predict() when calling predict.classify()

[colindean]

Fixes #113

This should enable a user to call predict() with options passed to tf.keras.Model.predict(), e.g.

nsfw_detector.predict.classify(model, input_paths, predict_args={'verbose': 0})

to disable Keras's progress bar or 2 instead of 0 in production, non-interactive execution.