docs(readme): tell users to also install grunt-cli/gulp-cli globally

closes angular-fullstack#1630

Author: javidrashid

Diff for: readme.md

@@ -16,9 +16,9 @@ Source code: https://github.com/DaftMonk/fullstack-demo
 
 ## Usage
 
-Install `yo`, `grunt-cli`, `bower`, and `generator-angular-fullstack`:
+Install `yo`, `grunt-cli`/`gulp-cli`, `bower`, and `generator-angular-fullstack`:
 ```
-npm install -g yo grunt-cli bower generator-angular-fullstack
+npm install -g yo grunt-cli gulp-cli bower generator-angular-fullstack
 ```
 
 Make a new directory, and `cd` into it: