修改 Group 和 Topic model

修改 Group 和 Topic model
Merge pull request #3 from amituofo/master

修改 Group 和 Topic model  merge
完成个人资料的修改功能
Merge branch 'master' of https://github.com/mutoulbj/BOHOO
+group form,copy 'avatar' to 'group_avatar'
完成新建群组
修复用户信息不能修改(忘记添加required=False)
Merge branch 'branch1'
Merge branch 'master' into branch1