导航条修改
前端大改动1
前端大改动2
前端大改动3
Merge branch 'master' of https://github.com/longshenzhu/COC into longshenzhu-master

Conflicts:
	demo_COC/accounts/forms.py
	demo_COC/accounts/models.py
	demo_COC/media/img/student/9/face.jpg
	demo_COC/templates/group/group.html
	demo_COC/templates/group/group_base.html
	demo_COC/templates/group/group_topic.html
before merge conflict
Merge branch 'longshenzhu-master'