Transforming Ember-cpm in an standard ember addon

Still a few details to polish, but almost done.

Although ember-cpm was already an ember-addon, it was structured it with broccoli and testem before ember-cli had support for addons, so everything was a bit taylor made a not very ember-ish (as we understood it now)

I really think that familiarity is an asset for the community, so I though that we we should that stick as much as possible to the defaults in the community. That way any newcomer that have ever used ember-cli will know how to contribute.

This meant:

* Use ember-cli as build/dev/test tool. No more make.
* Stick to standard jshint rules.
* Use QUnit for testing (tests are now modular and use the resolver).

It was pretty straightforward, so the only breaking changes are:

* EmberCPM no longer exposes `_utils` (which is fine, it never was intended to be public)
* I've structured all macros to be under `/macros` folder. That this makes more sense because it matches the public API (`EmberCPM.Macros.concat`). But this means that people requiring macros one by one like this `import concat from "ember-cpm/concat"` will need to change to  `import concant from "ember-cpm/macros/concat"`, so is mandatory to bump the 2nd digit of the version number.

### TODO
- [x] Update Readme
- [x] Update changelog
- [x] Write some integration tests to check everything is imported as expected in the dummy app.

### Future steps
- [ ] Upload builds to S3 on each successful build of the master branch.
I've revisited this piece of the readme to make it clearer for people that never used ember-cli.