GitLab

1. Solved by adding cast with tf.cast(predictions, tf.float64) at the point of
problem case.
2. Completed make_dataset() of automobile_data.py for the transforming of
DataFrame to Dataset, the standard one we know of official site.
3. Added from_dataset() in automobile_data.py for re-use by others sites in
cookbook/regression.

+ Removed try-except on `import pandas`, pandas is no longer optional here.