Extracted method to read call no of book since updating book availability does not need to update call no
Added NLBService#update_book to update the library statuses of an existing book
Book now creates libraries if they do not exist and updates library books collection upon both create and update
Added state_machine and hack for Rails 4.1 and added status to transition between queue and completed state. Queuing is currrently synchronous and needs specs as well