User Story #3: made shouldReturntitleauthoryear test pass in the BookTest.
User Story #3: added test for book with only title
User Story #3: reformatted library class to have a list of Book rather than a list of String, made shouldListOneBookWhenLibraryContainsOneBook pass
User Story #3: made shouldListTwo when Two pass
User Story #3: deleted unnecessary test
User Story #4:  Added MainMenu class and test.   shouldPrintListBooks as an options passes.