Adding NuGet badges to README

Author: abatishchev

README.md

@@ -1,5 +1,7 @@
 # StyleCop Analyzers for the .NET Compiler Platform
 
+[![NuGet](https://img.shields.io/nuget/v/StyleCop.Analyzers.svg)](https://www.nuget.org/packages/StyleCop.Analyzers)[![NuGet Beta](https://img.shields.io/nuget/vpre/StyleCop.Analyzers.svg)](https://www.nuget.org/packages/StyleCop.Analyzers)
+
 [![Join the chat at https://gitter.im/DotNetAnalyzers/StyleCopAnalyzers](https://badges.gitter.im/Join%20Chat.svg)](https://gitter.im/DotNetAnalyzers/StyleCopAnalyzers?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge)
 
 [![Build status](https://ci.appveyor.com/api/projects/status/8jw2lq431kgg44jl/branch/master?svg=true)](https://ci.appveyor.com/project/sharwell/stylecopanalyzers/branch/master)