message: Fix keras example to new keras API
diff: import tensorflow as tf
  import numpy as np
  -from tensorflow.contrib.keras.python.keras.models import Sequential
  -from tensorflow.contrib.keras.python.keras.layers import Dense, Activation
  -
  # Set variables to resource variables
  vscope = tf.get_variable_scope()
  vscope.set_use_resource(True)
  # Create Keras model
  -model = Sequential()
  -model.add(Dense(32, activation='relu', input_dim=100))
  -model.add(Dense(1, activation='sigmoid'))
  -#model.compile(optimizer='rmsprop', loss='binary_crossentropy', metrics=['accuracy'])
  +model = tf.keras.Sequential()
  +model.add(tf.keras.layers.Dense(32, activation='relu', input_dim=100))
  +model.add(tf.keras.layers.Dense(1, activation='sigmoid'))
  model.compile(optimizer='rmsprop', loss='binary_crossentropy')
  # Generate dummy data
  