!515 调整响应成功状态码为200,与全局保持一致

Merge pull request !515 from 武玉航/master

@@ -12,7 +12,7 @@ public class R<T> implements Serializable
     private static final long serialVersionUID = 1L;
 
     /** 成功 */
-    public static final int SUCCESS = 0;
+    public static final int SUCCESS = 200;
 
     /** 失败 */
     public static final int FAIL = 500;