This is just a link to the code of conduct at
http://www.dotnetfoundation.org/code-of-conduct which is already linked
to in the readme.
Putting it at this location just has github recognise it as such
(https://github.com/dotnet/corefx/community)
The text is the same as that used at
https://github.com/dotnet/docs/blob/master/CODE_OF_CONDUCT.md
