message: doc(CONTRIBUTING): Add note about msvs_version on Windows
  This adds a small note about setting the `msvs_version`
  in the npm config on Windows.
  Change-Type: patch
diff: @@ -40,6 +40,9 @@ You might need to run this with `sudo` or administrator permissions.
  C++ 2015` (see http://stackoverflow.com/a/31955339)
  - [MinGW](http://www.mingw.org)
  +You might need to `npm config set msvs_version 2015` for node-gyp to correctly detect
  +the version of Visual Studio you're using (in this example VS2015).
  +
  The following MinGW packages are required:
  - `msys-make`
  