Use tf.gfile instead of os.path in sequence_generator.py for internal compatibility. (#178)
Use tf.gfile instead of os.path in sequence_generator.py for internal compatibility. (#178)

* Fix index error in to_sequence when melody is empty.

* Use tf.gfile instead of os.path in sequence_generator.py for internal compatibility.

YoshikawaMasashi/magenta,YoshikawaMasashi/magenta,adarob/magenta,hanzorama/magenta,YoshikawaMasashi/magenta,jesseengel/magenta,magenta/magenta,YoshikawaMasashi/magenta,magenta/magenta,adarob/magenta,hanzorama/magenta,jesseengel/magenta