Generate CJS output during development builds.

This is not adding significant time, and it will likely be easier for
the SSR work.
Merge pull request #26 from rwjblue/generate-cjs-for-dev-builds

Generate CJS output during development builds.
version bump;
Adds tests for `ember-build`
Merge pull request #24 from twokul/tests

Adds tests for `ember-build`
Introduces concatenateES6Modules module

This PR abstracts the concatination of es6 modules.

If we ever need to upgrade/replace the way we concatenate
modules, we would need to replace only one `concateES6` module.
Merge pull request #28 from twokul/concatenate-es6-modules

Introduces concatenateES6Modules module