Make sure that AutoMapper.dll exists in output directory (in your case it is C:\Users\inelson\Documents\Visual Studio 2013\Projects\ClassLibrary4\ClassLibrary4\bin\Debug)
UPDATE: It is a well known problem with Portable Libraries and FxCop. Please, see answers:
- FxCop indirect reference to System.Core version 2.0.5.0
- Unable to resolve assemblies that use Portable Class Libraries
This problem also discussed in AutoMapper bugtracker.
UPDATE 2: And I'm pretty sure that problem appears because FxCop standalone version doesn't support .NET 4.5 and Portable Class Libraries. You can vote for appropriate suggestion on Visual Studio User Voice.
Did you try to run code analysis via Visual Studio?
UPDATE 3: I try to run 11.0.50727.1 version of FxCopCmd.exe which installed with Visual Studio 2012 (I found it at C:\Program Files (x86)\Microsoft Visual Studio 11.0\Team Tools\Static Analysis Tools\FxCop) and it seems to work.
Also, I try to run Code Analysis in Visual Studio 2012 and it also works.