VS2015 using the Nightlies

I have VS2015RC. I was looking to plug it into the nightly nuget feed. If i configure the normal way i don't get the intellisense from the nighly feed in project.json

i.e Nuget Package manager Settings

Also in the "Nuget Package Manager for Solution" if I change the package source to nightlies, nothing is listed, and it doesn't seem possible to check the "include prerelease" checkbox.

Are there any docs to show how to use the Nightlies with ASP.Net5 ?