updated readme with tool versions

Author: giograno

README.md

@@ -77,5 +77,12 @@ All the files with the metric values are available in [this](https://github.com/
 We also share the entire set of 18 projects used in the study [here](https://github.com/sealuzh/lightweight-effectiveness/tree/master/projects)
 
 ## Metrics Used
+A detailed list of the metrics used in this work is reported at this [link](https://github.com/sealuzh/lightweight-effectiveness/blob/master/metrics.md) or, alternatively, in the wiki page of this repository.
 
-A detailed list of the metrics used in this work is reported at this [link](https://github.com/sealuzh/lightweight-effectiveness/blob/master/metrics.md) or, alternatively, in the wiki page of this repository. 
+## Tool Versions 
+In this work we rely on the following tools:
+
+* PIT version 1.3.2
+* sciknit version 0.19.1
+* Maven version 3.5.0
+* Python version 3.6.4