Add monthsBeforeDate: and Add monthsAfterDate:
Merge pull request #6 from akuraru/add-monthsBeforeDate

Add monthsBeforeDate: and Add monthsAfterDate:
update run test script
Refactoring
bump 1.2.0
update for 1.2.0
about changelog
西暦で年を返す関数を追加。
昭和と平成で比較した場合のmonthsAfterDateのバグを修正