Update README.md

README.md

 # Renku MLS (machine learning schema) plug-in
 
-## Helping you benchmark
+## Helping you benchmark: user story
 
-If you have just got your feet wet with machine learning, you will soon realise
-that there are a myriad of techniques, models and metrics out there. Nowadays,
+As a scientist using machine learning packages, you will want to compare the 
+performance of different models and metrics for the same data. There are a 
+myriad of techniques, models and metrics out there. Nowadays,
 many popular machine learning packages out there, for example `scikit-learn`
 or `keras` have user-friendly interfaces in Python (or other languages).