EAK Migration Guide Update

This PR will update the EAK migration guide and sync it with the latest revision of ember-cli. How's next Monday sound for a deadline? Following is a list of updates that should be added, shout out any fixes/revisons/etc and I'll get them up ASAP, I'm just catching up too.

- [x] Should now use import Ember from 'ember' and import DS from 'ember-data'
- [x] Migrating the API Stub
- [x] Customizing the Express Server
- [x] Mention ember-cli-rest-api-blueprint
- [x] Update Cleanup section with app blueprint link