added initialize method the the Book class for attributes  author, title, id
corrected the spec so book takes 2 arguments for the test that checks for a default status and added a default status as available for the book class
created a checkout method in Book
modified check out method so it cannot be checked out twice
added the check_in method to the book class
created the intialize method for Borrower to create the name attribute
created the register new book method to the library class
created a check out method by id method in the Library class
created hash for library