TinyML Book Screencast #1 - Training the Hello World model

Screencast of the examples in Chapter 4 of the O'Reilly TinyML book on embedded machine learning. See https://tinymlbook.com for more details. Colab is at https://colab.research.google.com/github/tensorflow/tensorflow/blob/master/tensorflow/lite/micro/examples/hello_world/create_sine_model.ipynb New API is util.convert_bytes_to_c_source() at https://github.com/tensorflow/tensorflow/blob/master/tensorflow/lite/python/util.py#L390