Edit README to reference stable NuGet version

Author: asiffermann

README.md

@@ -1,6 +1,4 @@
-[![NuGet Pre Release](https://img.shields.io/nuget/vpre/GeekLearning.Templating.svg?maxAge=2592000&label=GeekLearning.Templating)](https://www.nuget.org/packages/GeekLearning.Templating)
-[![NuGet Pre Release](https://img.shields.io/nuget/vpre/GeekLearning.Templating.Handlebars.svg?maxAge=2592000&label=GeekLearning.Templating.Handlebars)](https://www.nuget.org/packages/GeekLearning.Templating.Handlebars)
-[![NuGet Pre Release](https://img.shields.io/nuget/vpre/GeekLearning.Templating.Mustache.svg?maxAge=2592000&label=GeekLearning.Templating.Mustache)](https://www.nuget.org/packages/GeekLearning.Templating.Mustache)
+[![NuGet Version](http://img.shields.io/nuget/v/GeekLearning.Templating.svg?style=flat-square&label=NuGet)](https://www.nuget.org/packages/GeekLearning.Templating/)
 [![Build Status](https://geeklearning.visualstudio.com/_apis/public/build/definitions/f841b266-7595-4d01-9ee1-4864cf65aa73/24/badge)](#)
 
 # gl-dotnet-templating