add a note about keras in tensorflow >= 1.4 (rasbt#47)

code/ch13/ch13.ipynb

@@ -870,6 +870,18 @@
     "import tensorflow as tf\n",
     "import tensorflow.contrib.keras as keras\n",
     "\n",
+    "# NOTE:\n",
+    "# ================================================\n",
+    "# If you have TensorFlow >= v1.4 installed\n",
+    "# you can use the keras API directly instead\n",
+    "# of importing it from the contrib module\n",
+    "# for instance, in this code cell, you can skip\n",
+    "# the import, and following code cells,\n",
+    "# you can use \n",
+    "# `tf.keras.utils.to_categorical(y_train)`\n",
+    "# instead of `keras.utils.to_categorical(y_train)`\n",
+    "# and so forth.\n",
+    "\n",
     "np.random.seed(123)\n",
     "tf.set_random_seed(123)"
    ]

code/ch13/ch13.py

@@ -11,6 +11,20 @@
 import struct
 import tensorflow.contrib.keras as keras
 
+# NOTE:
+# ================================================
+# If you have TensorFlow >= v1.4 installed
+# you can use the keras API directly instead
+# of importing it from the contrib module
+# for instance, in this code cell, you can skip
+# the import, and following code cells,
+# you can use
+# `tf.keras.utils.to_categorical(y_train)`
+# instead of `keras.utils.to_categorical(y_train)`
+# and so forth.
+
+
+
 # *Python Machine Learning 2nd Edition* by [Sebastian Raschka](https://sebastianraschka.com) and Vahid Mirjalili, Packt Publishing Ltd. 2017
 # 
 # Code Repository: https://github.com/rasbt/python-machine-learning-book-2nd-edition