[BUGFIX beta] Make Ember.RenderBuffer#addClass work as expected.
Pre-fill the ember.js tag in the SO link

Also change StackOverflow to Stack[space]Overflow, see the any page title or footer for proof.
Merge pull request #4274 from neeklamy/patch-1

Pre-fill the ember.js tag in the SO link
Merge pull request #4140 from ctimmerm/renderbuffer-addclass

[BUGFIX beta] Make Ember.RenderBuffer#addClass work as expected.
[FEATURE ember-runtime-test-friendly-promises]
Merge pull request #4176 from stefanpenner/friendly-promise-testing

[FEATURE ember-metal-test-friendly-promises]