Fixed issue with Owin delegate

[STRUDSO]

• Changed OwinStartupBase to use OwinHelpers extension method

I couldn't get the samples for owin to work, so i tried to change UseSimpleWeb to be compatible with "Owin" signature.

I could not get rake full to run, something with:
error: Could not find file: C:\src\fromgit\Simple.Web\src\Simple.Web.Razor.Tests.ExternalDummyAssembly\bin\Release\xunit
.dll

So seems like it's trying to run tests in ExternalDummyAssembly and failing on that because that assembly doesn't have a reference to xunit. I'm not that keen on rake/ruby but guees it should not try to run tests in ExternalDummyAssembly.

Please advice

[EddieGarmon]

It has not been decided that Func<AppFunc, AppFunc> is the OWIN middleware signature.

[beppler]

The following error is happening if using Microsoft.Owin.Hosting (version 2.1.0) with the actual implementation, this PR solves the problem.

[NullReferenceException: Object reference not set to an instance of an object.]
Microsoft.Owin.Builder.AppBuilder.ConvertOneHop(Type signature, Object app) +86
Microsoft.Owin.Builder.AppBuilder.Convert(Type signature, Object app) +90
Microsoft.Owin.Builder.AppBuilder.BuildInternal(Type signature) +265
Microsoft.Owin.Builder.AppBuilder.Build(Type returnType) +42

[ThatRendle]

I'll look at merging it. Just need to make sure it doesn't break Fix.

[BenPhegan]

Getting the same error trying to get a simple hello world app working. Did this (or another fix) make it in?