Added NuGet shield

Author: JoeTomkinson

README.md

@@ -4,6 +4,7 @@
 [![API](https://img.shields.io/badge/API-14%2B-orange.svg?style=flat)](https://android-arsenal.com/api?level=14s)
 [![License: MIT](https://img.shields.io/badge/License-MIT-blue.svg)](https://opensource.org/licenses/MIT)
 ![Build: Passing](https://img.shields.io/badge/Build-Passing-green.svg)
+[![NuGet](https://img.shields.io/nuget/v/Xama.JTPorts.EasingInterpolator.svg?label=NuGet)](https://www.nuget.org/packages/Xama.JTPorts.EasingInterpolator)
 
 [Xama.JTPorts.EasingInterpolator]