test/test_book.rb: fixed test to pass with ruby 1.8
test/test_book.rb: fixed test to pass with ruby 1.8

masawada/review,takahashim/review,murashitas/review,krororo/review,suzuki/review,orangain/review,kuad9/review_study,kmuto/review,orangain/review,suzuki/review,kuad9/review_study,krororo/review,masawada/review,kmuto/review,takahashim/review,krororo/review,kmuto/review,murashitas/review