Amended to README.md dependencies 

I have added two dependencies to README.md which should help people avoid a few problems I had when compiling the ndll.

I only had Visual Studio 2010 express installed which caused the compilation to fail. with this message:
"Cannot open include file: 'thread': No such file or directory". Stack overflow suggested upgrading to 2012 which fixed it: http://stackoverflow.com/questions/18367147/cannot-open-include-file-thread

I initially only installed the Windows SDK and not the developer toolkit which has the dll and some other includes.