message: docs: add travis status to README
diff: # Serverless Nextjs Plugin
  +[![Build Status](https://travis-ci.org/danielcondemarin/serverless-nextjs-plugin.svg?branch=master)](https://travis-ci.org/danielcondemarin/serverless-nextjs-plugin)
  +
  A serverless custom plugin to deploy nextjs serverless pages.
  The plugin targets Next-8 serverless mode. See https://nextjs.org/blog/next-8/#serverless-nextjs
  