Hi, thanks for posting.
At the time NCrunch 2.13 was released, VS2015 was only in an early preview state. There were a number of changes in VS2015 between this point and its final release, including the decommissioning/renaming of a whole version of the .NET framework. Unfortunately, these changes completely broke NCrunch.
For this reason, you'll need to use NCrunch 2.15 or above if you are to use NCrunch on the RTM version of VS2015.
Update: I've just adjusted the download page to remove the product download links for VS2015 for NCrunch 2.11-2.14. There's no point in having these online anymore, as they are just causing confusion and frustration. Sorry about this.