code.js

        $.ajax({
          beforeSend: function(xhrObj){
              xhrObj.setRequestHeader("Accept","application/json");
              xhrObj.setRequestHeader("Content-Type","application/json");
          },
          contentType: "application/json",
          type: "POST",
          url: "http://svel.to/links",
          data: '{ "links" : "http://emanuelcarnevale.com" }',
          processData: false,
          success: function(json){ //callback
                     jetpack.notification.show("url shortened");
                 }
        });

gistfile2.txt

Request Headers
Host	svel.to
User-Agent	Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10.5; en-US; rv:1.9.1) Gecko/20090624 Firefox/3.5
Accept	application/json
Accept-Language	en-us,en;q=0.5
Accept-Encoding	gzip,deflate
Accept-Charset	ISO-8859-1,utf-8;q=0.7,*;q=0.7
Keep-Alive	300
Connection	keep-alive
Content-Type	application/json; charset=UTF-8
X-Requested-With	XMLHttpRequest
Content-Length	43
Cookie	_shortamai_session=BAh7BzoPc2Vzc2lvbl9pZCIlMjhlZmMzYzM0Nzc4NDk4ZGM2MDBiYTg0Y2I5NzRmN2QiCmZsYXNoSUM6J0FjdGlvbkNvbnRyb2xsZXI6OkZsYXNoOjpGbGFzaEhhc2h7BjoKZXJyb3IiLENpIHNlbWJyYSBjaGUgaWwgdHVvIHVybCBub24gc2lhIHZhbGlkbwY6CkB1c2VkewY7B1Q%3D--aa70de663d2e1f6adeb203d6236658add41e15b9
Pragma	no-cache
Cache-Control	no-cache