wrapped resolve and reject in Ember.run, fixed specs

Wrapping resolve and reject in Ember.run will allow someone to sign in a user for integration testing.  Also, it was suggested [in this discussion](http://discuss.emberjs.com/t/guide-asynchronous-side-effects-in-testing/2905/11) that callbacks from libraries outside of ember itself be wraped in Ember.run.

This pull request also fixes the tests.

Thanks for the awesome plugin!