Update Backburner.js

Debounce was actually a throttle. Added a real debounce.
Better documentation for Ember.run.throttle and debounce
Improve Ember.Logger setup - Fixes #2962
Fix minor code style issues (missing semicolons)
Merge pull request #2979 from clbn/code-style-1

Fix minor code style issues (missing semicolons)
Removes an unused Ember.get include
Merge pull request #2981 from trek/remove-unused-get

Removes an unused Ember.get include