Convert to Ember CLI addon.

Fixes #8. I've converted this into an Ember CLI addon. I've made it to where you can specify which orbit files you want included in your environment.js file. I've updated the README but it the install instructions won't fully work until my pull request is accepted. Further, the instructions will change when it goes on npm.
Why was uglify downgraded here from what master is? https://github.com/orbitjs/ember-orbit/blob/master/package.json#L45