use error function for >= 400 codes

Author: fehguy

lib/http.js

@@ -90,7 +90,12 @@ SwaggerHttp.prototype.execute = function (obj, opts) {
   };
 
   obj.on.response = function(data) {
-    responseInterceptor(data);
+    if(data && data.status >= 400) {
+      errorInterceptor(data);
+    }
+    else {
+      responseInterceptor(data);
+    }
   };
 
   if (_.isObject(obj) && _.isObject(obj.body)) {