重新规划前后台的 css 和 javascript 目录结构

* 新建 javascripts/backend 目录，根据需要载入后台的 js 文件
* 新建 stylesheets/backend 目录，根据需要载入后台 css 文件
* 利用 backend.css 和 backend.js 载入所有文件
Upgrade bootstrape from 3.0.2 to 3.1.1
前端页面增加基础布局和样式

[Issue #55]

* 说明文件指定 ruby 2.1.0
* 创建前端页面布局文件和样式文件
* 默认首页暂时指向 frontend/products#index
添加 mobile 边栏切换效果

[Issue #55]

* add pushy jquery plugin
Merge branch 'feature/create_frontend' into develop
Merge pull request #56 from wjp2013/feature/create_frontend

Feature/create frontend
Merge branch 'develop' of github.com:wjp2013/SmartShop into develop

* 'develop' of github.com:wjp2013/SmartShop:
Base products list on frontend.

[Issue #57]
Server side pagination into a fancy infinite scroll.

[Issue #57]

* add `Infinite ajax scroll plugin`
删除 ajax 加载分页插件中不生效的功能
Merge branch 'feature/frontend_products_list' into develop
Merge pull request #59 from wjp2013/develop

Develop