cleans unused ref

Yavsc/src/Startup.cs

@@ -5,7 +5,6 @@ using System.IdentityModel.Tokens;
 using System.IO;
 using System.Reflection;
 using System.Security.Claims;
-using System.Threading.Tasks;
 using System.Web;
 using System.Web.Optimization;
 using AspNet.Security.OpenIdConnect.Extensions;
@@ -20,7 +19,6 @@ using Microsoft.AspNet.Diagnostics;
 using Microsoft.AspNet.FileProviders;
 using Microsoft.AspNet.Hosting;
 using Microsoft.AspNet.Http;
-using Microsoft.AspNet.Http.Authentication;
 using Microsoft.AspNet.Identity;
 using Microsoft.AspNet.Identity.EntityFramework;
 using Microsoft.AspNet.Localization;
@@ -37,7 +35,6 @@ using Microsoft.Extensions.PlatformAbstractions;
 using Microsoft.Extensions.WebEncoders;
 using Microsoft.Net.Http.Headers;
 using Yavsc.Auth;
-using Yavsc.Extensions;
 using Yavsc.Formatters;
 using Yavsc.Models;
 using Yavsc.Services;