Updating Newtonsoft.Json to 6.0.6

We use Json.NET to parse `project.json` for ASP.NET 5 projects. They use Json.NET 6 and the main issue is that they include single-line comments in the json files which is not supported in 5.x
Why do we need a redirect if we're directly using the new one throughout? Redirect only make sense if we're using some components that are bound to the old one and that we can't change.