项目显示以及others项目显示问题修复

	将unit_rate从Benefits 移动到了 Projects，并修改相应form中的输入项
	修改Project Model的SQL调用判断条件
	修改部分find_ongoing 为 find_all_ongoing
	修改others传入参数@projects：改为@projects[0,4]，即选取前四个
	modified:   app/controllers/application_controller.rb
	modified:   app/controllers/projects_controller.rb
	modified:   app/models/project.rb
	modified:   app/views/answers/_solution.html.haml
	modified:   app/views/benefits/_benefits_form_field.html.haml
	modified:   app/views/dashboard/main.html.haml
	modified:   app/views/mobile/questions/_question.html.haml
	modified:   app/views/past_projects/show.html.haml
	modified:   app/views/projects/_form_basic_info.html.haml
	modified:   app/views/projects/show.html.haml
	modified:   app/views/questions/_question.html.haml
	modified:   app/views/questions/show.html.haml
	new file:   db/migrate/20140611070216_move_unit_rate_to_project_domain.rb
4个，[0,4]代表从零开始选4个，基本上就是sub_str的用法