Update README.md

Author: charlesmartin14

README.md

@@ -200,6 +200,9 @@ with details provide for each slice for each layer.
 details = watcher.analyze(ww2x=True)
 ```
 
+#### Known issues
+
+rankloss is currently not working , may be always set to 0 
 
 
 [Demo Notebook](https://github.com/CalculatedContent/WeightWatcher/blob/master/WeightWatcher.ipynb)