Fix for "Cannot read property 'pkg' of null" error

    - The ember-cli-ember-data addon is deprecated
      switched the dependency to ember-data instead

Installed with npm from my local copy and it worked for me. I'm now being able to see "ember-data-django-rest-adapter" in info section of ember inspector

Not sure if it closes #6 as I wasn't able to reproduce this.

This means we now depend on ember-cli >= 0.4.5, but there are probably still issues with ember-data itself (1.0-BETA-10) and the adapter, so it's probably better to do a new release after this is done: https://github.com/toranb/ember-data-django-rest-adapter/pull/101