.NET Framework version for ASP.NET vNext apps on Azure

I'm just wondering what is the .NET Framework you should be using when building a website in Azure.

In Visual Studio 2015 RC, you can publish web projects to Azure. But how do you set up an Azure website?

I saw this post and I'm just wondering what is the MS reason for allowing vNext web apps (with class libraries using .NET 4.6) to publish to Azure when you can only select .NET 4.5 when setting up your site. Should I avoid using class libraries using .NET 4.6 in a vNext web application?