Add HTTP basic authentication.

lib/adapters/xhr.js

@@ -39,10 +39,17 @@ module.exports = function xhrAdapter(resolve, reject, config) {
     xDomain = true;
   }
 
+  // HTTP basic authentication
+  var configAuth = config.auth || {};
+  var auth = {
+    username: configAuth.username || configAuth.user || '',
+    password: configAuth.password || configAuth.pass || ''
+  };
+
   // Create the request
   var request = new adapter('Microsoft.XMLHTTP');
-  request.open(config.method.toUpperCase(), buildURL(config.url, config.params, config.paramsSerializer), true);
-  
+  request.open(config.method.toUpperCase(), buildURL(config.url, config.params, config.paramsSerializer), true, auth.username, auth.password);
+
   // Set the request timeout in MS
   request.timeout = config.timeout;