Update README.md

Tweak badge appearance

Author: BookOfGreg

README.md

@@ -3,7 +3,7 @@
 [![Gem](https://img.shields.io/gem/v/react-rails.svg?style=flat-square)](http://rubygems.org/gems/react-rails)
 [![npm](https://img.shields.io/npm/v/react_ujs.svg?style=flat-square)](https://www.npmjs.com/package/react_ujs)
 [![Build Status](https://img.shields.io/travis/reactjs/react-rails/master.svg?style=flat-square)](https://travis-ci.org/reactjs/react-rails)
-[![Maintainers Wanted](https://img.shields.io/badge/Maintainers-Wanted-red.svg)
+[![Maintainers Wanted](https://img.shields.io/badge/Maintainers-Wanted-red.svg?style=flat-square)]()
 
 
 React-Rails is a flexible tool to use [React](http://facebook.github.io/react/) with Rails. The benefits: