fix #158  use us-ascii as literal encoding explicitly
fix #158  use us-ascii as literal encoding explicitly

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