Sagemaker-containers

* Fix output_data_dir to reference an existing directory.
* Fix error message.
* Make pip install verbose.

* Fix error class for user script errors.
* Adding Readme.

* Improve logging
* Support for hyperparameters with JSON serialized and non serialized keys altogether
* Training Environment transforms to env vars
* Created beta framework entrypoint
* Filter SageMaker provided hyperparameters and user provided hyperparameters
* Script mode
* Cache module installation
* Support to requirements.txt
* Decoder/Encoder support for numpy, JSON, and CSV

* bug: Configuration: Change module names to string in __all__
* bug: Environment: handle hyperparameter injected by tuning jobs

* bug: Training: Move processing of requirements file out to the specific container.

* feature: TrainingEnvironment: read new environment variable for job name