WIP: Use Broccoli as build tool.

This is an initial attempt at moving the build process over to Broccoli.  It still needs work, mainly due to 1. the lack of plugin availability, 2. my lack of knowledge/experience with Broccoli.

- `grunt build`: Builds the library ready for distribution (lib.js and lib.min.js)
- `grunt server`: Starts test server at http://localhost:4200

Still missing:

- [ ] Commonjs dist. (There is a broccoli plugin which is still a WIP [broccoli-es6-module-filter](https://github.com/rpflorence/broccoli-es6-module-filter). Has many issues and is currently unusable).
- [ ] AMD dist non-concatenated and without loader. (Should also be doable with [broccoli-es6-module-filter](https://github.com/rpflorence/broccoli-es6-module-filter) once it's ready)
- [ ] Running tests using phantomjs or node (`grunt test`)