Batch Transformation example for xgboost_customer_churn

#740
@zxy844288792 @yuanzhua
Hi guys,

For our Customer Churn with Amazon Machine Learning example, Can I add another notebook to xgboost_customer_churn file using **batch transformation** to deploy GXBoost model, also slightly different feature engineering and model validation process?

Please let me know if worth to do it :) Thanks!