sharepoint 2013 Sp.Webproxy.invoke not include headers -

i working on sharepoint-hosted app needs call yammer rest api javascript. access token has been obtained. need pass in request headers. have use sharepoint cross-domain library in app.js. doesn't matter how tried, sp.webproxy calls endpoint without including header. turns out sharepoint intentionally ignores "authorizatio" header. know alternative approach? thank you.

function getyammer() {    var request = new sp.webrequestinfo();    request.set_url("https://www.yammer.com/api/v1/messages/algo.json");    request.set_headers({ "authorization": "bearer abcedfghijk" });     //headers not sent out external service   request.set_method("get");   var response = sp.webproxy.invoke(context, request);   context.executequeryasync(onsuccess, onfail);    function onsuccess() {     if (response.get_statuscode() == 200) {          removeposts('yammer');          var responsebody = json.parse(response.get_body());          (var = 0, len = responsebody.data.length; < len; i++) {             vm.addyammermessage(responsebody.data[i]);         }         sortpost();     }      else {         var httpcode = response.get_statuscode();         var httptext = response.get_body();         window.console && console.log("error code returned:" + httptext);     }   };    function onfail() {     window.console && console.log("get yammer messages failed:" + response.get_body());   }; 

};