After the recent update of NuGet to version 2.7 there seem to be some issues when creating a fresh install of Piranha CMS. Luckily there's a fairly simple workaround for this issue.
The package Piranha.Core is dependent on the ASP.NET MVC package from NuGet and when installing this package with previous versions of NuGet the runtime assembly versions are added to the Web.config. After the latest upgrade this section seems to be missing even though no updates have been made to any dependent packages. This causes exceptions when starting the application as the runtime don't know which assemblies to load.