Fix git tfs

Some fix on the tfs parts...

FYI:
* I'm one of the git-tfs developper and the one who has added branch support, among other things....
* My english is not perfect, so feel free to correct it ;) 
>Can you actually run git-tfs with VS Express if you have the SDK installed?

We've added the support of VS Express since they can connect to tfs with version 2012 ( https://github.com/git-tfs/git-tfs/pull/558 ). No need of the Visual Studio SDK. The sdk is needed only if you have no Visual Studio, just the .Net runtime and that you want to use git-tfs anyway (even if I don't know if someone is in this case...). I think it's enough even if I have not test on a clean computer...