updated usage example to readme

README.md

@@ -212,7 +212,7 @@ acmc phen copy -v v1.0.3
 	Use the following `acmc` command to compare the previous version (`v1.0.3`) with the latest version in the repository:
 
 ```bash
-python acmc.py phen diff -old ./workspace/v1.0.3/
+acmc phen diff -old ./workspace/v1.0.3/
 ```
 
 10. **Publish the phenotype at the next version**