* refactoring TransformersEstimator to support default and custom_hp * handling starting_points not in search space * addressing starting point more than max_iter * fixing upper < lower bug
* fixing bug for ner * removing global var * adding class for trial counter * adding notebook * adding use_ray dict * updating documentation for nlp
* xgboost gpu support * test xgboost gpu * test sparse data * add xgboost test * remove ray.init to avoid pytest error
