Implement Subsampled Smooth Calibration Error (SSCE)  from "Truthfulness of Calibration Measures"

Title: Truthfulness of Calibration Measures
Authors: [Nika Haghtalab](https://arxiv.org/search/cs?searchtype=author&query=Haghtalab,+N), [Mingda Qiao](https://arxiv.org/search/cs?searchtype=author&query=Qiao,+M), [Kunhe Yang](https://arxiv.org/search/cs?searchtype=author&query=Yang,+K), [Eric Zhao](https://arxiv.org/search/cs?searchtype=author&query=Zhao,+E)