Streamed responses can be be Object or Stream

See issue aspnet#518

Author: nicemd

src/Microsoft.AspNetCore.NodeServices/HostingModels/HttpNodeInstance.cs

@@ -91,7 +91,7 @@ protected override async Task<T> InvokeExportAsync<T>(
 
                 case "application/octet-stream":
                     // Streamed responses have to be received as System.IO.Stream instances
-                    if (typeof(T) != typeof(Stream))
+                    if (!typeof(T).GetTypeInfo().IsAssignableFrom(typeof(Stream).GetTypeInfo()))
                     {
                         throw new ArgumentException(
                             "Node module responded with binary stream. This cannot be converted to the requested generic type: " +
@@ -136,4 +136,4 @@ protected override void Dispose(bool disposing)
             }
         }
     }
-}
+}