Remove IncludedConfigurationProvider since it's been added to Configuration repo

src/Microsoft.AspNet.Hosting/Internal/IncludedConfigurationProvider.cs

@@ -1,39 +0,0 @@
-// Copyright (c) .NET Foundation. All rights reserved.
-// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
-
-using System;
-using Microsoft.Extensions.Configuration;
-
-namespace Microsoft.AspNet.Hosting.Internal
-{
-    // TODO: Remove this once https://github.com/aspnet/Configuration/pull/349 gets merged
-    internal class IncludedConfigurationProvider : ConfigurationProvider
-    {
-        public IncludedConfigurationProvider(IConfiguration source)
-        {
-            if (source == null)
-            {
-                throw new ArgumentNullException(nameof(source));
-            }
-            int pathStart = 0;
-            var section = source as IConfigurationSection;
-            if (section != null)
-            {
-                pathStart = section.Path.Length + 1;
-            }
-            foreach (var child in source.GetChildren())
-            {
-                AddSection(child, pathStart);
-            }
-        }
-
-        private void AddSection(IConfigurationSection section, int pathStart)
-        {
-            Data.Add(section.Path.Substring(pathStart), section.Value);
-            foreach (var child in section.GetChildren())
-            {
-                AddSection(child, pathStart);
-            }
-        }
-    }
-}