Fixed http reference.

Author: Oren (electricessence)

README.md

@@ -2,7 +2,7 @@
 
 Provides a set of useful classes when implementing a disposable.
 
-[![NuGet](http://img.shields.io/nuget/v/Open.Disposable.svg)](https://www.nuget.org/packages/Open.Disposable/)
+[![NuGet](https://img.shields.io/nuget/v/Open.Disposable.svg)](https://www.nuget.org/packages/Open.Disposable/)
 
 ## Core principles