Add X-PJAX-Selectors header

lib/send-request.js

@@ -61,6 +61,7 @@ module.exports = function(location, options, callback) {
   request.timeout = timeout
   request.setRequestHeader("X-Requested-With", "XMLHttpRequest")
   request.setRequestHeader("X-PJAX", "true")
+  request.setRequestHeader("X-PJAX-Selectors", JSON.stringify(options.selectors))
 
   // Send the proper header information for POST forms
   if (requestPayload && requestMethod === "POST") {