Update the install instructions for a typical notebook>=5.3 case.

Author: jasongrout

{{cookiecutter.github_project_name}}/README.md

@@ -9,16 +9,21 @@
 
 ## Installation
 
-A typical installation requires the following commands to be run:
+You can install using `pip`:
 
 ```bash
 pip install {{ cookiecutter.python_package_name  }}
-jupyter nbextension enable --py [--sys-prefix|--user|--system] {{ cookiecutter.python_package_name  }}
 ```
 
-Or, if you use jupyterlab:
+Or if you use jupyterlab:
 
 ```bash
 pip install {{ cookiecutter.python_package_name  }}
 jupyter labextension install @jupyter-widgets/jupyterlab-manager
 ```
+
+If you are using Jupyter Notebook 5.2 or earlier, you may also need to enable
+the nbextension:
+```bash
+jupyter nbextension enable --py [--sys-prefix|--user|--system] {{ cookiecutter.python_package_name  }}
+```