Backbone Boilerplate 2.0.0

- Integrates PureCSS framework opting out of HTML5 Boilerplate.
- Adds in template loading via RequireJS AMD plugin.
- Restored `grunt test` which lints and run unit tests.
- Upgraded Bower dependencies (RequireJS and Chai).
- Removed coveralls as it's caused more builds to fail than pass.
- Organized Grunt tasks into **build/tasks** folder.