修改数据库表结构，修改日期字段类型改为字符串，长度为20
Merge branch 'master' of https://github.com/duanhp/EnglishPlus
衍生单词表增加衍生规则，数据字典增加动词过去式
增加类库设计说明文档
Merge pull request #5 from mawb/master

shejiwendang
Merge pull request #1 from duanhp/master

HHHHH
Merge pull request #6 from mawb/master

设计文档
Merge branch 'master' of https://github.com/duanhp/EnglishPlus into duanhp-master

Conflicts:
	Script/DB/EnglishPlus
模块分工