:bug: 修复某些情况下会抛出CannotResolveClassException异常错误的问题

https://stackoverflow.com/questions/9508292/nodecom-thoughtworks-xstream-mapper-cannotresolveclassexception-while-using-xstr

weixin-java-pay/src/main/java/com/github/binarywang/wxpay/bean/result/BaseWxPayResult.java

@@ -150,6 +150,7 @@ public abstract class BaseWxPayResult {
     }
     XStream xstream = XStreamInitializer.getInstance();
     xstream.processAnnotations(clz);
+    xstream.setClassLoader(BaseWxPayResult.class.getClassLoader());
     T result = (T) xstream.fromXML(xmlString);
     result.setXmlString(xmlString);
     return result;