fixes #104 id of image files in opf file includes directory name
fixes #104 id of image files in opf file includes directory name

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