add _linear_function to Stree

First try to implement predict_proba with sigmoid based on Platt

README.md

@@ -1,8 +1,15 @@
 # STree
+
 Oblique Tree classifier based on SVM nodes
 
 ## Example
 
+## Jupyter
+
+[Binder link to test.ipynb](https://gesis.mybinder.org/binder/v2/gh/Doctorado-ML/STree/80b5cf8e722a0fc648624fbab69cd686847f906d)
+
+## Command line
+
 ```python
 python main.py
 ```