Fixing #171, don't fail on error responses with json payloads

lib/adapters/xhr.js

@@ -72,7 +72,7 @@ module.exports = function xhrAdapter(resolve, reject, config) {
         config: config
       };
       // Resolve or reject the Promise based on the status
-      ((request.status >= 200 && request.status < 300) || (request.responseText && xDomain) ?
+      ((request.status >= 200 && request.status < 300) || (xDomain && request.responseText) ?
         resolve :
         reject)(response);