Book module

Steps:
- Create a API module in the Node.js app (751e40f)
  * Define the model and export it ([`book.model`](https://github.com/aliou/tsundoku/blob/books/app/api/books/book.model.js))
  * Define the controller method needed ([`book.controller`](https://github.com/aliou/tsundoku/blob/books/app/api/books/book.controller.js))
  * Finally, create the router to serve the controller method ([`router`](https://github.com/aliou/tsundoku/blob/books/app/api/books/index.js))
- Create an angular module:
  * Create the provider route
  * Create the controller getting the books
  * Create the template to show the books
Return an error message too.