update book's action

@all: Phần này hơi dài (mặc dù nó chỉ là trang view book), các anh chịu khó xem giúp em nhé :3
Bảng join tên sai convention.
http://book.cakephp.org/2.0/en/getting-started/cakephp-conventions.html
```Join tables, used in hasAndBelongsToMany (HABTM) relationships between models, should be named after the model tables they will join, arranged in alphabetical order (apples_zebras rather than zebras_apples).```