Pysurvival

* Correcting typo in setup.py

* Fixing Survival Forest models splitrule

* Finalizing the doc-strings and tutorials.
* Rewriting the code so that the parametric models use PyTorch 1.0 (https://pytorch.org/docs/1.0.0/).
* All the survival forest models (https://www.pysurvival.io/models/survival_forest.html) were added.

* Initial release