Dispose the service provider on app shutdown

- Added a unit test

#322

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

@@ -32,6 +32,7 @@ namespace Microsoft.AspNet.Hosting.Internal
         public void Dispose()
         {
             _stop.Dispose();
+            (_services as IDisposable)?.Dispose();
         }
     }
 }

test/Microsoft.AspNet.Hosting.Tests/Fakes/FakeService.cs

@@ -1,7 +1,17 @@
 // 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;
+
 namespace Microsoft.AspNet.Hosting.Fakes
 {
-    public class FakeService : IFakeEveryService { }
+    public class FakeService : IFakeEveryService, IDisposable
+    {
+        public bool Disposed { get; private set; }
+
+        public void Dispose()
+        {
+            Disposed = true;
+        }
+    }
 }

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

@@ -7,6 +7,7 @@ using System.Collections.Generic;
 using System.IO;
 using System.Threading.Tasks;
 using Microsoft.AspNet.Builder;
+using Microsoft.AspNet.Hosting.Fakes;
 using Microsoft.AspNet.Hosting.Internal;
 using Microsoft.AspNet.Hosting.Server;
 using Microsoft.AspNet.Hosting.Startup;
@@ -92,6 +93,32 @@ namespace Microsoft.AspNet.Hosting
             Assert.Equal(1, _startInstances[0].DisposeCalls);
         }
 
+        [Fact]
+        public void HostingEngineDisposesServiceProvider()
+        {
+            var engine = CreateBuilder()
+                .UseServer(this)
+                .UseServices(s =>
+                {
+                    s.AddTransient<IFakeService, FakeService>();
+                    s.AddSingleton<IFakeSingletonService, FakeService>();
+                })
+                .UseStartup("Microsoft.AspNet.Hosting.Tests")
+                .Build()
+                .Start();
+
+            var singleton = (FakeService)engine.Services.GetService<IFakeSingletonService>();
+            var transient = (FakeService)engine.Services.GetService<IFakeService>();
+
+            Assert.False(singleton.Disposed);
+            Assert.False(transient.Disposed);
+
+            engine.Dispose();
+
+            Assert.True(singleton.Disposed);
+            Assert.True(transient.Disposed);
+        }
+
         [Fact]
         public void HostingEngineNotifiesApplicationStarted()
         {