Updated Builder constructors

src/Microsoft.AspNet.AppBuilderSupport/AppBuilderSupportExtensions.cs

@@ -16,7 +16,7 @@ namespace Owin
     {
         public static IAppBuilder UseBuilder(this IAppBuilder appBuilder, Action<IBuilder> configuration)
         {
-            IBuilder builder = new Builder();
+            IBuilder builder = new Builder(null);
             configuration(builder);
             Func<AppFunc,AppFunc> middleware1 = next1 => {
                 Func<RequestDelegate,RequestDelegate> middleware2 = next2 => {

test/Microsoft.AspNet.PipelineCore.Tests/BuilderTests.cs

@@ -8,7 +8,7 @@ namespace Microsoft.AspNet.PipelineCore.Tests
         [Fact]
         public void BuildReturnsCallableDelegate()
         {
-            var builder = new Builder();
+            var builder = new Builder(null);
             var app = builder.Build();
 
             var mockHttpContext = new Moq.Mock<HttpContext>();