Update package.json

Make things look nice on https://www.npmjs.org/package/ember-cli-font-awesome and on http://addons.builtwithember.io/

Currently looks like this:
![screen shot 2014-09-09 at 11 12 56 am](https://cloud.githubusercontent.com/assets/61048/4204024/cda887ba-3833-11e4-84e9-7058c3e2e34c.png)