查看的资料:http://www.cnblogs.com/zyw-205520/p/4950357.html
compile 'com.mcxiaoke.volley:library:1.0.19'
http://www.tuicool.com/articles/eeyQ3eE
http://blog.csdn.net/guolin_blog/article/details/17482095
https://github.com/android-cn/android-open-project-demo/tree/master/volley-demo