Added go report badge

Readme.md

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 <p align="center"><a href="http://isomorphicgo.org" target="_blank"><img src="https://github.com/isomorphicgo/isogoapp/blob/master/static/images/isomorphic_go_logo.png"></a></p>
 
 # Isomorphic Go App (isogoapp)
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+[![Go Report Card](https://goreportcard.com/badge/github.com/isomorphicgo/isogoapp)](https://goreportcard.com/report/github.com/isomorphicgo/isogoapp)
 
 A basic, barebones web app, intented to be used as a starting point for developing an [Isomorphic Go](http://isomorphicgo.org) application.