Survivaleval

Fix the no module found error in the package.

Fix the dependency issues. Remove the `python` version and `jupyter` in the requirements.txt file.

Improve the readme files in the distribution package

Format the package to prepare for the official PyPI submission

1. Add the single time evaluator class
2. minor revision for AUC
3. minor changes for Brier score if the training information is not available
4. remove unnecessary dependencies, keep the main package as light as possible

2024-04-28:
Add the non-IPCW-weighted Brier score and IBS.

2024-03-13:
Remove the `rpy2` dependency. Now the package is pure python.