Enforce coding style

This PR adds jscs with basic config file inspired of jQuery CS standards and improve code readability and consistency by following these CS rules.

JSCS check is available through `grunt jscs` command and automatically launched on `build`.

I also cleaned the `package.json` by removing unnecessary prod-dependancies and moving them to dev-dependancies.

Finally, jshint and jscs are now automatically launched with `grunt test` to enforce coding style rules and code quality hover upcoming pull requests.