Add C#/.net implementation

Hi @dascritch, 
I've added a C# implementation. I've tested this implementation with your test suite. However, I did not include a test file. I would like to start a discussion about how you would like to test.

It seems that your test suite is executed on a *nix environment. You can execute C#/.Net through Mono on these platforms. However, I suspect that most of devs who will clone this repo will never use this C# implementation :).

One solution may be to publish an independant BaseRefCSharp repository on GitHub. That way, we can also add : 
* A proper support for MSTest/xUnit test framework
* NuGet package generation (it's like npm for .net)