Machine Learning Pathway Classifier Example (cognoma#39)

* adding machine learning example

* updating ml example for pull request comments

* updating ml example 1

* add neo4j-driver to environment

* add neo4j pathway example

this commit creates an example pipeline to build a classifier to detect a Hippo signalinggene expression signature. It queries hetnet pathways and generates a Y matrix for any sample with a mutation for any gene in the hippo pathway

* nbconvert example to .py

* update pathway script

I address all pull request comments in the update

* update pathway example py

nbconvert updated pathway notebook

* remove download logic and rename

* remove hardcode tissue filter output