[BUGFIX beta] IE8 fixes for beta

6 failures left to go. Everything major seems to be locked down, though this also requires that https://github.com/tildeio/htmlbars/pull/91 be merged and the dependency in Ember be updated.

* [x] Update the dependency to HTMLBars
* [ ] Triage the final 5 failure with @rwjblue, fix anything remaining
* [ ] Make Travis happy

Review of this and the HTMLBars PR very welcome.
lgtm. dropped this commit.