* Added Xgboost support
* Added DataframeHandler options includes 'typ', 'input_columns', 'orient'
* BentoML cli command now supporst json string as input, e.g. --input="{"col": {"0": "bc"}}"
* BentoML cli command now supports input file from s3, e.g. --input=s3://my-bucket/test.csv
* Added gunicorn support, serve-gunicorn is now default in generated Docker image
* Added `ver` decorator for specifying versions with [semantic versioning](https://semver.org/)