add books_controller
remove unused file.
add book factory
add feature spec for books
refactor books_controller_spec
add image_url column
impliments listing books
add kaminari
add paging
add isbn10 and isbn13 length validater
add space between limit symbol and limit value
adjust FactoryGirl define to pass book.isbn validation
add test case for isbn validator
rename describe description .page -> pagination
narrowed the scope to pass test case page.should have_selector
delete unused files
modify isbn validation
modify features spec(request spec)
add validation of image_url length and modify book_spec
add view paginate book