Update README.md (aurelia#727)

Nikolaj Ivancic · EisenbergEffect · commit b87bdadbc9b8 · 2016-12-07T20:59:12.000-08:00
diff --git a/skeleton-esnext/README.md b/skeleton-esnext/README.md
@@ -54,7 +54,7 @@ To run the app under [Electron](http://electron.atom.io), follow these steps.
 1. Install [Electron](http://electron.atom.io)
 
   ```shell
-  npm install electron-prebuilt -g
+  npm install electron --save-dev
 ```
 
 2. From the project folder, execute the following command:
