Uses the same timeout error message on XHR adapter than HTTP adapter

lib/adapters/xhr.js

@@ -78,7 +78,10 @@ module.exports = function xhrAdapter(resolve, reject, config) {
 
   // Handle timeout
   request.ontimeout = function handleTimeout() {
-    reject(new Error('Timeout'));
+    var err = new Error('timeout of ' + config.timeout + 'ms exceeded');
+    err.timeout = config.timeout;
+    err.code = 'ECONNABORTED';
+    reject(err);
 
     // Clean up request
     request = null;