Adding cancellation support

lib/adapters/xhr.js

@@ -153,6 +153,15 @@ module.exports = function xhrAdapter(config) {
       request.upload.addEventListener('progress', config.onUploadProgress);
     }
 
+    if (config.cancelToken) {
+      // Handle cancellation
+      config.cancelToken.promise.then(function onCanceled(cancel) {
+        request.abort();
+        reject(cancel);
+        // Clean up request
+        request = null;
+      });
+    }
 
     if (requestData === undefined) {
       requestData = null;