Android Support v4、v7、v13 介绍
google提供了Android Support Library package 系列的包来保证来高版本sdk开发的向下兼容性，即我们用4.x开发时，在1.6等版本上，可以使用高版本的有些特性，如Fragement,ViewPager等，下面，简单说明下这几个版本间的区别：
Android Support v4: 这个包是为了照顾1.6及更高版本而设计的，这个包是使用最广泛的，eclipse新建工程时，都默认带有了。Android Support v7: 这个包是为了考虑照顾2.1及以上版本而设计的，但不包含更低，故如果不考虑1.6,我们可以采用再加上这个包，另外注意，v7是要依赖v4这个包的，即，两个得同时被包含,最新的Support V7包也开始支持ActionBar了
Android Support v13:这个包的设计是为了android 3.2及更高版本的，一般我们都不常用，平板开发中能用到。
http://developer.android.com/tools/support-library/features.html
v7 appcompat library
This library adds support for the Action Bar user interface design pattern.
v7 gridlayout library
This library adds support for the GridLayout class, which allows you to arrange user interface elements using a grid of rectangular cells. For detailed information about the v7 gridlayout library APIs, see the android.support.v7.widgetpackage in the API reference.
This library is located in the <sdk>/extras/android/support/v7/gridlayout/ directory after you download the Android Support Libraries. This library contains user interface resources. To include it in your application project, follow the instructions for adding libraries with resources.
v7 mediarouter library
This library provides MediaRouter, MediaRouteProvider, and related media classes that support the Google Cast developer preview.
In general, the APIs in the v7 mediarouter library provide a means of controlling the routing of media channels and streams from the current device to external screens, speakers, and other destination devices. The library includes APIs for publishing app-specific media route providers, for discovering and selecting destination devices, for checking media status, and more. For detailed information about the v7 mediarouter library APIs, see the android.support.v7.mediapackage in the API reference.
The v7 mediarouter library is located in the <sdk>/extras/android/support/v7/mediarouter/ directory after you download the Android Support Library. It's provided as a library project with a dependency on the v7 appcompat library, so you'll need to include both libraries in your build path when setting up your project. For more information on how to set up your project, follow the instructions in adding libraries with resources. If you are developing in Eclipse/ADT, make sure to include both the android-support-v7-mediarouter.jar and android-support-v7-appcompat.jar files.