Add missing NPM package file to project Module 4

See Module 4 video at: 0:21:35 @sedouard failing to run npm install. The `package.json` is still empty prior to this PR

![20141226180613](https://cloud.githubusercontent.com/assets/14539/5558487/ea6e3ba6-8d29-11e4-9bd8-3f86fe74baa7.jpg)