Updated node minimal version requirement after...

...angular 4 update

README.md

@@ -14,7 +14,7 @@ If you're looking for the 2016 Angular 2 DSpace UI prototype, you can find it [h
 Quick start
 -----------
 
-**Ensure you're running [Node](https://nodejs.org) >= `v5.x`, [npm](https://www.npmjs.com/) >= `v3.x` and [yarn](https://yarnpkg.com) >= `v0.20.x`**
+**Ensure you're running [Node](https://nodejs.org) >= `v6.9.x`, [npm](https://www.npmjs.com/) >= `v3.x` and [yarn](https://yarnpkg.com) >= `v0.20.x`**
 
 ```bash
 # clone the repo