1.8 support

Once this PR is finalized, I'll lint the entire project and fix the tests failing on phantomjs.

I've removed all the innerHTML logic and now let ember handle all of the rerendering logic.  I'm not sure it's as performant, but it's definitely cleaner and less jumping through hoops.

Tests pass in chrome, fail on phantomjs. Before I fix those, I want to hear @stefanpenner and @mixonic 's opinion if this is the direction to go.

Demo: http://jsbin.com/rawevaleco/1/edit

/cc @mixonic @stefanpenner 
Agreed, was going to send a PR to add `observerOnce` since this is a pattern that gets annoying to type out