Sync book edition and repo

[bougwal]

The book Reactive Programming with Angular and ngrx is awesome. Yet the way code snipptes are represented affects its value. It would be excellent to have a new edition to meet the updates in this repo and also to enhance the way code is introduced. Theoretically, it clarifies the concepts well. Practically, the reader is lost since the book reference code snippets and paths that does not exist anymore (or it seems to be).