Update install_and_test.md

install_and_test.md

@@ -29,10 +29,10 @@ pip install git+ssh://git@git.ia2.inaf.it/hotwheels/PM.git@v0.0.0alpha
 # If you need to put hands on the source code
 
 In case you find that you need to edit the source code of hotwheels (maybe you found a bug), you
-can re-install a python module in editable mode. For instance, let's suppose that now you need to edit the timestep module and re-run all tests. You can do the following 
+can re-install a python module in **editable mode (use -e in pip install)**. For instance, let's suppose that now you need to edit the timestep module and re-run all tests. You can do the following 
 
 ```bash
-pip install git+ssh://git@git.ia2.inaf.it/hotwheels/timestep.git@v0.0.0alpha 
+git clone ssh://git@git.ia2.inaf.it/hotwheels/timestep.git
 cd timestep
 # very IMPORTANT the -e will install in editable mode
 # so you can change the module code and effects will take place