Wrapped body with has a x-handlebars template.

The TodoMVC tutorial wasn't working after step "displaying-model-data" because the http://emberjs.com/guides/getting-started/creating-a-static-mockup/ step didn't include this from the start. It is in the Live Preview but this might confuse beginners.
Merge pull request #1000 from hbarroso/patch-1

Wrapped body with a x-handlebars template.