+
+ * - resume: int, byte offset to start the download from;
+
+ * if the server supports ranges
+
+ * - maxfilesize: int, maximum file size that should be downloaded;
+
+ * has no effect, if the size of the requested entity is not known
+
+ * - lastmodified: int, timestamp for If-(Un)Modified-Since header
+
+ * - timeout: int, seconds the request may take
+
+ * - connecttimeout: int, seconds the connect may take
+
+ * - onprogress: mixed, progress callback
+
+ * - ondebug: mixed, debug callback
+