加入微信接口中时间类型的序列化转换类，供转换json使用

weixin-java-mp/src/main/java/me/chanjar/weixin/mp/bean/WxMpXmlMessage.java

@@ -6,6 +6,8 @@ import java.io.Serializable;
 import java.util.ArrayList;
 import java.util.List;
 
+import com.fasterxml.jackson.databind.annotation.JsonSerialize;
+import me.chanjar.weixin.mp.util.json.WxLongTimeJsonSerializer;
 import org.apache.commons.io.IOUtils;
 import org.apache.commons.lang3.builder.ToStringBuilder;
 import org.apache.commons.lang3.builder.ToStringStyle;
@@ -47,6 +49,7 @@ public class WxMpXmlMessage implements Serializable {
   private String fromUserName;
 
   @XStreamAlias("CreateTime")
+  @JsonSerialize(using = WxLongTimeJsonSerializer.class)
   private Long createTime;
 
   @XStreamAlias("MsgType")