158 appveyor

A bunch of fixes for running Kentor.AuthServices on AppVeyor for #158
 - Set up NuGet package restore on solution
 - Configure git for CRLF endings
 - Specify test assembly to not run VSPremium tests
 - Note about setting up AppVeyor for contributors

An AppVeyor project of my personal fork building this branch is available on https://ci.appveyor.com/project/albinsunnanbo/authservices