规范package，为发布到maven central repository做准备

src/main/java/me/chanjar/weixin/bean/custombuilder/ImageBuilder.java

@@ -0,0 +1,31 @@
+package me.chanjar.weixin.bean.custombuilder;
+
+import me.chanjar.weixin.api.WxConsts;
+import me.chanjar.weixin.bean.WxCustomMessage;
+
+/**
+ * 获得消息builder
+ * <pre>
+ * 用法: WxCustomMessage m = WxCustomMessage.IMAGE().media_id(...).touser(...).build();
+ * </pre>
+ * @author chanjarster
+ *
+ */
+public final class ImageBuilder extends BaseBuilder<ImageBuilder> {
+  private String media_id;
+
+  public ImageBuilder() {
+    this.msgtype = WxConsts.CUSTOM_MSG_IMAGE;
+  }
+
+  public ImageBuilder mediaId(String media_id) {
+    this.media_id = media_id;
+    return this;
+  }
+
+  public WxCustomMessage build() {
+    WxCustomMessage m = super.build();
+    m.setMedia_id(this.media_id);
+    return m;
+  }
+}