Update README.md

Author: pwelter34

README.md

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 [![NuGet Version](https://img.shields.io/nuget/v/EntityFrameworkCore.Generator.svg?style=flat-square)](https://www.nuget.org/packages/EntityFrameworkCore.Generator/)
 
+[![Coverage Status](https://coveralls.io/repos/github/loresoft/EntityFrameworkCore.Generator/badge.svg)](https://coveralls.io/github/loresoft/EntityFrameworkCore.Generator)
+
 ## Features
 
 - Entity Framework Core database first model generation