0.3.0

This release enhances the OBP package in the following ways.

• allowing evaluation policy to be stochastic, which makes the package more consistent with the formulation of OPE
• adding some advanced estimation techniques such as cross-fitting and doubly robust with shrinkage
• modifying examples to evaluate offline bandit policies (not online ones), which again makes the package more consistent with the formulation of OPE: https://github.com/st-tech/zr-obp/tree/master/examples
• adding some slides: https://github.com/st-tech/zr-obp/tree/master/slides