Refactor Brocfile vendor package loading.
Move ember package to packages_es6.
ES6ify ember package.
Include ember package in Brocfile.
Do not export Ember.Application from ember-runtime.

This is causing an issue with load order. If ember-application package
is loaded first, then ember-runtime is loaded we will actually clobber
the correct Ember.Application with the completely skinnied down version
in Ember Runtime.