add new,create method at books_controller
fixed routes
add  "add Book" button in books/index.html.erb
add new method at books_controller
add new html at books
add create method at books_controller
add omniauth-twitter to Gemfile
add OmniAuth initialize script
add new,create,destroy method at sessions_controller
add link to twitter auth
add after twitter callback method at routes
add create method at sessions_controller
remove unnecessary statement
modify book column
modify take information