Exception handling in the AppDomainAssemblyTypeScanner when read an unmanaged code library

With the new Assembly type scanner, when nancy search for the libraries containing references to Nancy, when tries to load a assembly that is not (for example SQLite.Interop.dll or libzmq.dll) the method LoadAssembliesWithNancyReferences from the class AppDomainAssemblyTypeScanner throw a BadImageException. 

This pull request only add a try-catch to handle the BadImageException and don't provoke to shutdown the current process and pass to load the next assembly.

Thanks.