use ember-cli as the CLI to build ember. (broccoli under the hood)

Such dog-fooding.

bonus, ember-cli now comes with  broccoli-sane-watcher, which dramatically reduces the cost of file system watching.

Enjoy your battery life!
Merge pull request #4982 from stefanpenner/ember-cli

use ember-cli as the CLI to build ember. (broccoli under the hood)