React to HttpAbstractions changes

test/Microsoft.AspNet.Hosting.Tests/WebApplicationTests.cs

@@ -558,11 +558,21 @@ namespace Microsoft.AspNet.Hosting
             {
             }
 
+            public TFeature Get<TFeature>()
+            {
+                return default(TFeature);
+            }
+
             public IEnumerator<KeyValuePair<Type, object>> GetEnumerator()
             {
                 yield break;
             }
 
+            public void Set<TFeature>(TFeature instance)
+            {
+                throw new NotSupportedException();
+            }
+
             IEnumerator IEnumerable.GetEnumerator()
             {
                 yield break;