Added ChemicalX and RexMex

ChemicalX and RexMex were added.

README.md

@@ -1065,6 +1065,8 @@ be
 <a name="python-general-purpose-machine-learning"></a>
 #### General-Purpose Machine Learning
 
+ * [RexMex](https://github.com/AstraZeneca/rexmex) -> A general purpose recommender metrics library for fair evaluation.
+ * [ChemicalX](https://github.com/AstraZeneca/chemicalx) -> A PyTorch based deep learning library for drug pair scoring
  * [Microsoft ML for Apache Spark](https://github.com/Azure/mmlspark) -> A distributed machine learning framework Apache Spark
  * [Shapley](https://github.com/benedekrozemberczki/shapley) -> A data-driven framework to quantify the value of classifiers in a machine learning ensemble. 
  * [igel](https://github.com/nidhaloff/igel) -> A delightful machine learning tool that allows you to train/fit, test and use models **without writing code**