[BUGFIX beta] Upgrade Backburner to 0.2.0
[BUGFIX beta] Ember.onerror now uses Backburner's error handler - #3401
Merge pull request #4562 from emberjs/backburner-upgrade

[BUGFIX beta] Upgrade Backburner, Switch Ember.onerror to Backburner's handler
[BUGFIX beta] Total invalidation of arrayComputed by non-array dependencies should be synchronous