Update Startup.Auth.cs

I think this area should be commented out SocialLogins aren't setup since START-HERE doensn't describe the steps yet. 
Leaving this uncommented results in an Error about ClienId option that should be provided.
![server error clientid](https://cloud.githubusercontent.com/assets/9781801/5063902/4723b6d6-6dfa-11e4-88ec-e1b31545aa25.png)

ConfigurationManager?? This is something that I don't know of. Where can someone set an appsetting like EnableSocialLogins???
Anyway this helps too... :-)