named export instead of default export

Author: itaditya

README.md

@@ -9,7 +9,7 @@ $ npm install @probot/serverless-lambda
 
 ```javascript
 # handler.js
-const serverless = require('@probot/serverless-lambda')
+const { serverless } = require('@probot/serverless-lambda')
 const appFn = require('./')
 module.exports.probot = serverless(appFn)
 ```