Update Ember and Handlebars

Ember: 1.0.0-rc6.1
Handlebars: 1.0.0
Remove symlinks, downgrade Handlebars and specify Handlebars version

* GitHub doesn't want to serve symlinked scripts (for obvious reasons)
* Handlebars needs to be 1.0.0-rc.4 to work with Ember 1.0.0-rc.6
Change paths to external JS assets
Start of Emberification