[Build] Add info for building on VS 2015 to readme.md

Author: xoofx

Readme.md

@@ -11,6 +11,7 @@ You can find more documentation on the [Wiki](http://sharpdx.org/wiki)
 ## Build
 
 In order to compile SharpDX, you need to install the [Windows 10 SDK 10.0.10586.0](https://dev.windows.com/en-us/downloads/windows-10-sdk)
+You need also to install Visual Studio 2015 with the checked option "Tools for Windows 8.1"
 
 ## Samples