make a failing test: no destroy reviewed books

gem 'database_cleaner'
bundle install
add a features dir to spec
books_spec.rb
add some failing destroy specs
Merge branch '13-no-destroy-with-reviews' into nodelete-tests
pass published author indestructible test

add a destroyable? method
check destroyable? in controller .destroy
has_many :books, :dependent => :restrict_with_exception
pass tests: book and author no destroy rules (#9)

gem 'capybara' # to visit pages in rspec
bundle install
book:
add a destroyable? method
check destroyable? in controller .destroy
has_many :reviews, :dependent => :restrict_with_exception
Merge pull request #89 from nbirnel/nodelete-tests

Nodelete tests