add npm badge

Author: Rwing

README.md

@@ -1,4 +1,6 @@
 # node-csharp-random
+[![npm version](https://badge.fury.io/js/node-csharp-random.svg)](https://badge.fury.io/js/node-csharp-random)
+
 a random library like as Random Class of C#
 ```
 var Random = require('node-csharp-random');
@@ -21,4 +23,4 @@ console.log(random.NextDouble());
 
 ![random-node](https://raw.githubusercontent.com/Rwing/Rwing-s-Repository/master/images/random-node.png)
 
-![random-csharp](https://raw.githubusercontent.com/Rwing/Rwing-s-Repository/master/images/random-csharp.png)
+![random-csharp](https://raw.githubusercontent.com/Rwing/Rwing-s-Repository/master/images/random-csharp.png)