Update README.md

README.md

@@ -30,6 +30,7 @@ If you want to install the development version, checkout the `dev' branch and th
 ```bash
 git clone git@gitlab.ecosystem-modelling.pml.ac.uk:fvcom/pyfvcom.git ./PyFVCOM
 cd PyFVCOM
+git checkout dev
 pip install --user -e .
 ```