修改项目图片显示
	修改辅助函数：
		modified:   app/helpers/application_helper.rb
		modified:   app/models/project.rb
	修改项目界面模版：
		modified:   app/views/layouts/project.html.haml
	修复答题页面其他项目链接图片问题：
		modified:   app/views/projects/_others.html.haml
Merge branch 'master' of https://github.com/ProgrammerYuan/dazuoxiaoti.com