Update Reference_BeeWatch.md
Merge pull request #16 from genedna/patch-1

Update Reference_BeeWatch.md
Merge pull request #17 from genedna/master

修改格式错误
Merge pull request #18 from genedna/master

修改数据库字段中文档中关于auto_now和auto_now_add的错误，为unique和datetime增加示例代码。
Merge pull request #19 from genedna/master

增加设置数据库字段为 null 的代码示例。
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Merge pull request #21 from luxuchu/patch-5

Update Controllers_Filters.md
Merge pull request #1 from beego/master

同步最新的版本beego文档