Compress + Mangle minified output.
Merge pull request #564 from rjackson/use-better-uglify-options

Compress + Mangle minified output.
ensure brocfile added deps are added after internal deps

fixes -> https://github.com/stefanpenner/ember-cli/commit/64ee626649aa39943b1ba327c8d8ac4d55e773e3#commitcomment-6189670
Refactor to commands and tasks taking dependencies via constructor options. Paving the way for dependency injection.
Update custom errors instructions
Add `app.import` to control legacy files, remove broccoli-bower.