More developer-friendly Ember builds

[a13o]

The Ember TodoMVC app is currently minified, with sourcemaps disabled. This makes it difficult to browse the code from the todomvc website using devtools.

I would like to modify the Ember build config so that it doesn't minify and it contains sourcemaps.

This is in the spirit of the README:

We intentionally use the unminified versions to make reading the source code easier.