AFNetworking单张图片上传

//仅作为学习笔记

这里如果没有235行，可能会上传失败，失败错误：

 { status code: 200, headers {

    "Content-Length" = 14;

    "Content-Type" = "text/plain;charset=utf-8";

    Date = "Thu, 22 May 2014 10:37:50 GMT";

    Server = "Apache-Coyote/1.1";

    "Set-Cookie" ="JSESSIONID=C0DFED60A154557F8386E62AB2A066CE; Path=/FHJRDT";

    } }, NSLocalizedDescription=Request failed:unacceptable content-type: text/plain}