Update README.md

Author: jcoady

labextension/vpython/README.md

@@ -16,31 +16,17 @@ jupyter labextension install vpython
 
 ## Development
 
-For a development install use the instructions for creating a custom jupyter labextension as a guide:
-
-https://jupyterlab.readthedocs.io/en/stable/developer/extension_tutorial.html#extension-tutorial
-
-but taylor the instructions for creating a vpython labextension.
+For a development install (requires npm version 4 or later), do the following in the repository directory:
 
 ```bash
-jlpm install
-jlpm add @jupyterlab/application
-jlpm add @jupyterlab/apputils
-jlpm add @jupyterlab/coreutils
-jlpm add @jupyterlab/docregistry
-jlpm add @jupyterlab/notebook
-jlpm add @phosphor/disposable
-jlpm add script-loader
-
-cp -r ../../vpython/vpython_{libraries,data} .
-jlpm run build
+npm install
+cp -r ../../vpython/vpython_{libraries,data} lib/
 jupyter labextension install .
 ```
 
 To rebuild the package and the JupyterLab app:
 
 ```bash
-jlpm run build
+npm run build
 jupyter lab build
 ```
-